Hi and welcome.

They didn't use acid in the very beginning, but it was introduced for etching the Maltese cross on a few items in the '70s. I have no idea what the 1000 means.
To tell glass from resin, if you take a hot pin or needle to the base, resin will melt, smoke or smell. Glass won't.
And glass should feel cool to the touch, resin would be warm, then there is the weight, glass would be heavier.