This is a golden ring, and a temporary transformation does not change its Essential Nature, so I don't think you can use the Shape and Material bonuses.
I think you could engrave your ruby with a shape, to add another bonus, but another material would require another component.
Your number of components is limited by your Magic Theory. If you followed the advised minimum of 3, you should be able to make it a hornbeam bow with a ruby-set golden ring on it.
Then you can have an enchantment to make it disappear into the ring when you don't need it
This wouldn't work for most standard purposes* - something has to be an actual shape, not just a representation of a shape.
*There are a few things it would work for - Potent Magic can use representations, and the Rusticani Craft Magic virtue lets you have a bonus from a representation equal to half the standard bonus for standard lab work (pg 132 of HoH:S) .
I don't think the original question is one the Rules deal with specifically anywhere, so it's a question of coming up with a consistent solution your troupe finds reasonable (or just avoiding the issue).
This is disputed. In The Mysteries page 89, in the box discussing normal talismans we have
The crown on the coin is mentioned. Why mention it if it is not relevant to the shape/material bonuses.
On a more fundamental level, the notion of representations of objects allowing connections to the realm of forms for that object feels to me to be one of the fundamental rules of magic. I can't see an easy way to argue against it.
I feel like this branched off really fast. I can Muto a rock talisman into a representation of anything with a cantrip. It shouldn't suddenly become an omni-talisman with every shape bonus I can think of when I have a spare season to add a new bonus to it.
Yeah, sorry I got the representation-as-shape bit wrong.
I think that using Muto to change a shape and get a different bonus goes against the Limit of Essential Nature, if only because it allows access to unlimited shapes and makes the choice of a Shape for your Talisman component pointless.
Allowing shapes feels abusive. I think I'll go with first shape determines them all.
Which still means it can make sense to create a a staff talisman, even if you really want it to be a bow or a ring 90% of the time, because the boni are better.
Ya, I could turn a staff into a ring and use it's staff bonuses because it's essential nature is a staff. I probably couldn't do that with a door or bed since they use specifically passing through and sleeping in to describe their bonuses. I suppose there is an argument to be made for everything else needing to interact with the world as it's essential form, wands direct spells because you point with them or what ever.