You could put a little 50/50 nitric in one of those small cavities, like on the right in pic#2. Let it set for awhile and then transfer the solution into a beaker with a squirt bottle. Test the solution with weak HCl or salt water for AgCl.
You could also test the surface with Schwerter's solution. Ag gives a red color
In the photos, it looks like it could be nickel plate, especially in pic#3. Silver is the whitest metallic element there is. Nickel could be confirmed by dissolving in nitric, making the solution ammoniacal, and using DMG. However, be aware that, if it is Ag plated, there is a good chance that there is nickel plate under the silver. This could confuse the issue.
You might be able to peel a little of the plate by tapping an area with a ball peen hammer. If the plating can be made to stretch laterally, it will pop loose.
You might be able to flake some of the plating off by using a little 50/50 HCl in one of those cavities. If the plating is porous at all, the HCl could undermine the plating, attack the Al, and flake off the plating. If the HCl readily attacks the metal, with no plating flakes observed, it is probably unplated Al.
If it is silver plated, the best way I can think to strip it is in nitric acid. Most Al alloys won't be attacked, but some will, especially when the solution gets hot. Although most references say that Al isn't attacked by HNO3, I have seen it happen under certain conditions or with certain alloys. If nitric works without attacking the Al, I would probably strip them one by one in an open top plastic drum and then drain them well and dip them in a couple of rinses.
EDIT: I just thought of this. Nitric might not work at all. The Al, if it is soluble at all, might reduce the silver back to metal as fast as you can dissolve it. If it is silver plate and, if nitric won't work, you might just have contaminated aluminum, unless someone can come up with another way to strip the silver.
I have stripped Au from Al in the electrolytic conc. sulfuric cell with no attack on the Al. You could strip Ag with this but, with all the cavities on those parts, you could have a mess. Also, you would have to figure out how to get the Ag out of the stripper.
Do you see any peeling where the torch was applied? Heating will often pop the plating loose.
