A texas made Colt Dragoon pattern revolver (made for the Confederates, was shown on Antiques Roadshow this past year. It was in non-working condition with cosmetic damage to the backstrap, broken percussion cap nipples and non-functional lockwork. It's value was appraised at around $40,000 and the owner was advised not to attempt repair.
Now personally, if I could get it's internals exposed without affecting the condition of the screws, finish, etc. I might be inclined to have a competent gunsmith (experienced at such antique revolvers) to attempt to restore the gun to function, so long as doing so would not involve changing any parts, etc. At the least, conservative care to ensure the revolver doesn't degrade any further would be worthwhile.
Now, as far as the Sendra is concerned, I might be inclined to mount a different upper to prevent degrading the original, but on the other hand, why not shoot it?