Plexiglass Coin Holder

PVC in it's "natural" state is hard, brittle and translucent. It's also cheap, which is why people used it. But to make it soft, pliable and transparent (like you often find in cheap coin album pages) they have to add plasticizers. It's these plasticizers that degrade over time, leaving hydrochloric acid behind. This acid eats away at any coins placed inside them, creating the classic "PVC green slime film" you see on coins left in such albums for too long.

The green slime can be washed off with acetone, but the damage has been done - a lustrous or mirror-proof coin will appear hazed, a bright copper coin will darken, and so forth.

Plexiglass, also known as polymethylmethacrylate (PMMA), lucite, acrylic glass, and various other trade names, should be perfectly safe, at least for the short and medium term. PMMA, or a similar substance, is what the TPGs use when they slab coins.

When it comes to any type of plastic if your not sure the simplist method it to contact the manufacturer. Many people just guess what something may or may not really be and the results too are sometimes just guesswork. What you call Plexiglass may be almost anything.
Does it state Plexiglass anywhere on that item? Is there a manufacture's name anywhere? If you could find the name of the manufacturer, contact them, via pnone if possible. Then naturally do as they all do today and state "This conversation may be recorded for your safety". Then ask about your product as to the safety of your coins. I have an old plexiglass holder for a type set and found who made it and called them. There is a really large variety of all plastic products so it always is safer and smarter to contact the people that really know.