Hi agreeneyes ... As Ironlord mentions, if it is cut glass, crystal, or etched, then the edges of the relief are sharper than if it is pressed glass. With my fingers having been used to smooth out cement, scratching around in the ground in the garden, and having been abused in a thousand different ways over the years, they're not as sensitive, so when I find a piece of glass and I'm not sure what it is, I gently rub it against my wrist or forearm, which are more sensitive, and I can normally tell ...if it runs over the skin smoothly,. it's 'probably' pressed, molded.
That will normally (but there are exceptions) make a massive difference to the value of the item.