Unlock the Recalcitrant Door (ReTe 5)
R:Touch, D:Mom, T:Part
By touching a locked or barred door, it is unlocked or the bar moved so that it can be opened. Works on doors up to 10 feet tall, but also on chests. Casting requisite appropriate to the Form of the locking mechanism is required (usually Herbam for wooden bars). An heavily deteriorated locking mechanism may resist being unlocked, requiring a Int+Finesse roll against an Ease Factor from 6 to 15, depending on how badly damaged it is.
(Base 1, +2 metal, +1 Touch, +1 Part)
I considered unlocking the door a natural movement for it, but since many locks are made of metal I added 2 magnitudes. Used Part range because the lock is not the whole door, and the mechanism may not be accessible from the outside.
There's actually exactly that spell on page 78 of City and Guild, except that it's called "The Key of Theodorus" and erroneously has the part magnitude adding +2 for a total level of 10.
I hadn't seen it, but it is indeed almost identical. However, The Key of Theodorus does not seem to cover doors barred from the inside (by an actual wooden beam or a simple metal latch). Would this spell be a reasonable alternative? It's not as good with damaged locks, but a bit more flexible for barred doors.
If the only function is to open a lock as if you had the key, I'm fine with the spell -- and indeed I'd remove the Part modifier, targeting the Individual lock rather than a Part of the door. So Base 1, +2 Metal, +1 Touch, yielding a Level 4 Rego Terram spell (possibly with casting requisites depending on the material of the lock)
However, if the door is held fast by a bar, a latch or even a lock only accessible from the other side of the door, so that one on the caster's side would not be able to open it even with a key, well... it gets tricky. Ultimately it depends on whether the bar/latch/clasp/lock can be considered part of the door or not. In some cases it's clear, in others not so much.
If it can, then a similar spell would work, but it would have to operate on the whole door, because you are obviously not sensing the bar, so you cannot target it without an arcane connection. I'd add casting requisites for all components of the door (usually Herbam). I'd also add 1 magnitude because it's "slightly unnatural" to open from the outside a door that can only be opened from the inside; this is very subjective, but to me it "feels right". So Base 2, +2 Metal, +1Touch, yielding a Level 5 Rego Terram spell.
However, if the blocking mechanism is inaccessible from outside and not part of the door, I do not think you'd be able to target it with a spell like yours; even though there are many workarounds. One would be using Target:Room to unlock all the entrances of the Room you are touching (which adds 2 magnitudes). So Base 2, +2 Metal, +1Touch, +2 Room, yielding a Level 15 Rego Terram spell. Of course, this does not work if the magus is inside a cell, barred from the outside.
If it's a question of opening and closing a door Hermetic magic doesn't even have to worry about it being locked. Rego can move the door from one natural state (closed) to another natural state (open) without having to worry about any barriers in between (locks or bars), like teleportation. Of course a bar that occupies the space the door occupies when opened would potentially prevent that; it wouldn't prevent transporting the door 5 paces away though.
Edit: Also, can't you consider the whole door including all locking mechanisms as Part of the building they are in? That should let you effect everything all at once.
If we'resuggesting alternate effect, I'd go with Pass the Unyielding Portal (ArM5 p. 137).
I think Part is actually correct, since it's only parts of the lock that are manipulated.
Actually, I am seeing any normal locking mechanism (either a lock or a bar) as part of the door, hence the suggested Target.
If it's something else blocking the door, or preventing it from being opened (such as a pile of lumber stacked against it, or rockfall, or whatever not part of the door), then the spell won't work. It affects the door, essentially changing its state from "unopened" (locked or barred) to "openable" by moving part(s) or it naturally (lock mechanism, or sliding the latch/bar).
Bear in mind that if you want to affect bars and such, you need a herbam requisite because ReTe is not going to move that wooden bar.
Terram can move solid stuff, not only earth-stone-metal based ones. I always found that debatable, but it is clearly stated in the rules.
Casting requisite, as stated in the spell's description.