A test for damascus can be done @ home (outside), after cleaning (degreasing & sanding a small spot on the barrel(s), hidden under the forearm wood.
A swipe with copper sulfate (on a Q-tip) will show any damascus figure very quickly.
There are three main sources of copper sulfate:
One is from commercial products sold in local fish stores specifically to treat snail infestations.
The others are from hardware stores (gardening section- a treatment for pests and fungal infections in plants)
from pharmacies (as a disinfectant).
IIRC, original-type repro buttplates are available from Connecticut Shotgun's catalog. (Google)