u/Belgium1418

I got these two in a large lot of 19th and early 20th century coins. Does anyone know more about them?

Hi everyone!

I am planning to replace all of the cardboard 2×2 flips in my collection with these double sided ones.

For context: I collect and study coins minted in Zeeland (province of the Netherlands) between 1555 and 1806. The cardboard holders are a problem for multiple reasons. Taking coins out to weigh, measure, compare... is a pain in the ass. With the stapled holders it's doable but annoying, for the self adhesive ones, I have to use a new holder every time. A second problem is that because a lot of these coins are relatively thin, the plastic is too loose, causing it to be slightly wrinkled and giving issues with visibility (especially with some of the darker toned copper coins). And lastly, some of the coins I get from older collection have holders that are damaged, worn... I do replace those with new ones, but I'm sure this issue will keep repeating itself as the holders I use also get worn.

I want to switch all of those out and use these guardhouse double coin flips, which also makes it easier to keep a card with information with the coin. I noticed there are two different kinds: unplasticised pvc, and polypropylene. These are more rigid, which helps greatly with the visibility of the coins, and I can take the coins out whenever I need to without having to replace the holders every time.

Now, my question is, are the unplasticised pvc ones fine? They are sold as 'ideal for mid to long term storage' while the PP ones are sold as 'archival'. I have some of the upvc ones already, that I got from a friend who uses these, and they're not the cheap flexible pvc ones, but I'm curious if the PP ones are better. I'm not in the US, and the PP flips are only available on the guardhouse site, so I'm curious if it's worth the extra shipping + import/export taxes to get the PP ones, or if it's fine to get the uPVC ones locally.