Wizards Key ReTerr10 +18
--Base 2 (control in unnatural way), +1 Touch, +2 Metal, +1 Precision
--Unlocks doors barred with metal bars or locks.
One of my new players wants this spell.
Part of me says... "Bars? Well, you can't touch the bar on a door if you're outside it."
The other part says... "God's wounds, man! You're killing the fun in the game!"
What say you all?
You can add an Herbam casting requisite if he can't actually touch the mechanism. He affects the object as a whole, an Herbam entity.
I think it's a bit pedantic... but true, so I'd keep to it.
I'd say too fussy. You can touch the door. The door has a metal bar or lock.
I'd make it Part Target though. You are effecting a part of the door. On the other hand, hand I'm not sure that you need the +1 for precision...but perhaps you do.
I don't think it needs a Herbam requisite. The lock/bar is metal. The door can be made of anything --- stone, metal, wood, corpus, whatever.
My view is that you have to touch the lock not the door. You aren't opening the door but manipulating the lock only. This is just my view and it gives a logical limit to a low level spell that is very powerful (esp if the mage decides to go thieving).
Considering person can't see the target they are trying to effect because it is on other side of the door, I think this is very reasonable.
With spells like Obliteration of the metallic barrier in existence, I see no reason why a wizard's Key spell would be so unbalancing. What mundane door could possibly stop a wizard?
As far as formuli go though, I would rewrite it in a clearer form...
Wizard's Key
ReTe 15
Base 2 (slightly unnatural fashion), +2 metal, +1 touch, +1 Part (locking mechanism would only be part of a door or gateway), +1 complexity (to allow use on all locks/portcullises from simple to complex).
Open sez ME! 
Of course taking the entire "must sense the target to affect it" paradigm into equal consideration, I might argue the need for an additional (and preliminary) spell that would allow the magus to see through the door/gate to ascertain if indeed there are any bars/portcullis to deal with beyond the locked door/gate before opening the initial door/gate and giving guards time to prepare a rebuff.
Wizard's Window
PeIm(He) 10
base 4(destroy an object's ability to affect sight), +1 Touch, +1 Diameter
By use of this spell, all wooden doors/gates become transparent to any would be interloper.
Insofar as this second spell is Herban req specific, it will not hinder the successful targeting of the initial door's/gate's locking mechanism and could in fact aid the caster in apprehending the internal lock mechanism buried inside the wooden door/gate.
Rather elementary spell casting possible even for an apprentice (and likely a popular one amongst many Tytalean apprentices.)
The target is the door (part); as long as you can sense the door I think that you should be fine.
For comparison you could create a touch range spell that turns a person's hair blue. There is no suggestion in the rules that you have to actually touch the person's hair to do this --- touching the person is fine. Equally, there is no suggestion that this spell would be defeated if the target is wearing a hat; sensing the person is enough, you don't need to sense their hair too.
There was a 4th edition spell that did exactly that. IIRC the first place where I saw it was a Flambeau starting character in the mysteries that had the dogue of venice as an enemy and a focus in Light (a really cool focus to move a little step out of the normal fire focus).
The spell was exactly what has just been described: ReTe15. Can't recall the exact RDT, but it was pretty close.
As an alpha SG, I would say that to me this is a perfectly valid spell from a game and metagame perspective. Go for it 
BoXer's version looks perfectly kosher to me.
Cheers,
Xavi
Thanks Richard, but I can assure you I understand the concepts of "Part" and "Target". 
Apparently you have misunderstood what I was saying to the OP in the paragraph you quoted. To clarify, I would draw your attention back to the original post in which he says:
I took this as referring to doors/gates with metal locks AND those which might also be backed with some manner of iron grating or portcullis for reinforced security (such as the main gate of a castle or manor).
The OP goes on to write:
Which I took (beyond its literal meaning) as intimating the classic "must be sensed to be affected" paradigm. Of course I might have read too much into that sentence, but if not then a preliminary spell to see through the door would facilitate subsequent ReTe targetting of otherwise heretofore undetected iron bars/grates/portcullises.
Cheers
B
I'd agree with Yair's Herbam requisite, by analogy with the Corpus requisite to affect something inside the human body where you cannot see it (e.g. create water in the lungs).
Thinking of the bar as being a part of the door only serves to reinforce that idea.
There is no need for a +1 for complexity, though. It's still a pretty simple action. At best, you'd ask for a finesse roll, not raise the level of the spell.
depends on the nature of the lock. If you can waggle your finger inside the mechanism then you can touch the mechanism itself.
From what i remember, keys at this time were little more then punch cards.
Just a thought:
If bars could not be targeted by spells, as they cannot be sensed, they would become THE device of security any magus would use on his sanctum. Still, you could turn the door into dust or knock it down, but this will leave clear signs someone intruded.
However, this way you can only use bars when inside your sanctum, as you cannot lift it yourself from the outside...
That is, unless you enchant the bar itself to unlock when YOU say the command word.
I'd just add one magnitude (+5) for fancy effect. It's a game and not a question of doctrine.
I like this version better unlocking a door where the bar is on the other side. This is also level 15, not level 10, the boost in magnitude I think is more balanced. I suspect though that you will need a herbam requisite since many doors and bars are wood, not steel or metal.
Fair enough. Maybe I'm misunderstanding you...
But I think, if you can target the lock of a door as a Part of the door (which I think is absolutely fine), then you don't need to sense the lock separately to sensing the door itself.
If you can sense the door, you can target any of its parts.
Similarly, if you can Touch the door, then you don't need to Touch the individual Part that the spell targets. Touching the door itself is good enough.
For example, I could imagine a Touch range, Corpus spell with a Part Target that stops the beating of someone's heart. I don't think that it is necessary for the caster of this spell to sense the person's heart (sensing the person is good enough), it's also not necessary to first open their chest cavity so that you can actually Touch their heart (touching the person is good enough).
Once again, that isn't what I was saying in the slightest. What I am referring to is the OPS comment about ALSO targetting bars which would be ON THE OTHER SIDE of the door, thus out of sight under normal circumstances.
With the prelimary spell I suggested, a magus could not ONLY see and target the visible lock in the door (Target:Part) but could also target any secondary bars/grates/portcullises behind the door since he could now see through the door.
He/she would also know, by means of the transparency spell, whether he might be suddenly facing a line of archers in the castle entryway as soon as he got the first door open but before he/she could get off a second ReTe spell to lift/open the secondary iron barrier to let the fighting grogs and companions or army storm into the castle.
Do you understand my thinking now?
Oh, I see, things that are not Part of the door?
Sure, if you want to target those you need to sense them. But then you can't target them with a Touch range spell anyway --- as the door is in the way (unless you can also reach through the door with magic somehow). And you can't target them with a Part target spell, as they are not Part of the door either.
If the bar is attached to the door (I am thinking an iron bar attached to the back of the door, and the wall), then it can be targetted fine with Part effects that target the door...you only need to sense the door. Even if the bar is on the other side from you, and you can't see it, this is fine. You can sense and touch the door, so you can affect its parts.
On the other hand, if the iron bar is behind, but separate to the door, or there is a portcullis behind the door, then the bar/portcullis is not a Part of the door. So, yes, you need to sense the portcullis separately to sensing the door. You need to actually touch the portcullis to affect it with a Touch range effect. You cannot affect the portcullis by casting a Part target spell on the door; because the portcullis is not a Part of the door.
Richard, perhaps I am misreading your tone, but you really do come off as overly pedantic.
I am well aware of the fact that a secondary barrier, perceived via the transparent door spell, could not be affected at Touch Range unless the initial door/gate was opened first. Do you take me for a complete idiot?
The ReTe spell posited by the OP was obviously created with Touch Range based on the understanding that the secondary bar was Part of the door. If one wanted an all in one spell to unlock AND unbar the door/gate AND/OR lift a secondary portcullis then the Range would need to be at least Voice and better Sight with a Group Target to account for all the disparate Parts.
Notwithstanding that, I merely suggested the transparent door precursor spell (given the OP's choice of Touch Range ReTe) in order to know in advance:
To satisfy your need for exactitude then,
Wizard's Master Key
ReTe lvl 20
Base 2 (control in a slightly unnatural fashion), +2 voice, +2 metal, +2 Group
Of course, this is a momentary version which suffices to open the lock and lift any secondary bar/latch as well as the portcullis (if there is one) but will not hold the portcullis up presuming its own mechanism is not in the "raised" position. To be absolutely sure of unhindered entry one would need to add at least a Concentration or Diameter Duration to the affect making it level 25, still doable for any halfway decent journeyman magus/maga.
I see no reason why any magus so predisposed to such gate crashing might not have both Part and Group versions of the spell in their repertoire.
YMMV
I hope we can put this exchange to bed now.
No.
Yes, the transparent door spell might be useful for all the reasons that you say. But to solve the original problem it isn't required.