National Prisoner Of War Museum Silver Coin

It may? could? be silver plated, with a copper alloy core.
That is the most probable possibility with a medal such as this.

There is no indication of a silver weight or purity.

If it was silver is should say the purity of the silver.

The medal (vs. coin) you've shown is definitely similar in design to the official 1994 US Prisoner of War silver commemorative dollar struck by the US Mint, but it is a privately-struck piece (i.e., not a Mint product).

As you've pointed out, it lacks the date as well as the inscriptions "Liberty" and "In God We Trust" on the obverse. On the reverse, it is missing the denomination and "P" mint mark. The Mint did not produce any silver dollars that were missing these elements.

The piece also lacks the designer's initials on both sides.

As already mentioned, it might have been a souvenir sold in the museum's bookstore/gift shop in the years following the coin's 1994 release. One reason I'm not fully convinced of this, however, is the fact that it uses the artwork of the original coin w/o crediting the original designers. When you consider that the museum is a US National Park and that it received funds from the sales of the official commemorative silver dollar to help build it, it seems a bit unlikely that an uncredited knock-off of an official Government product would be sold in the museum's store (but anything is possible).

As others, I question whether it is solid silver vs. being silver plated - the lack of markings indicating its purity and weight is often a telltale sign that the item is not pure silver.