I have many old "Library of Coins" albums that are copyright 1958 by the Coin and Currency Institute. Here is one example:

The coins in them have been there for upwards of 60 years. In the cent albums the plastic slides seem to be hard plastic (suspect no PVC - and the copper coins are not turning green). The later albums, eg. the dollars, the plastic inserts are a little more flexible.
Does any one have experience with these?
Is it safe to continue using them?
In the Morgan books I have noticed some coins with toning around the edges. As stated earlier, the copper coins are not turning green.
Would it be advisable to stop using them? Then extract the coins and put them into 2x2 flips?
Thanks!