There are enough fakes of those types that slabbing would make them easier to sell, and they seem to be in relatively good condition. I can't speak for the authenticity--some of the fakes are pretty good. If you don't plan to sell them in the near future, it may not be worth doing anything unless you are just curious to see the results. Never hurts to check weight/magnetism before you send them in to make sure you aren't wasting your time/money. I never had my one yen graded (I think I have 2 or 3) because they are chop marked, and in worn enough condition to be unlikely to be faked. You used to be able to get these for about US $20, but prices have come up a lot since the 90s.
For me just to get it encapsulated and labeled. Value would suggest it to be worth it. Those chop marks add character. I like it.
Normally when I see Asian silver crowns these days, they are not genuine. However this time, I'm quite certain that they are both genuine. While common (ish), they should command easily 100+ each. Nice one!
Just to add on The Japanese yen is dated 1904 and the Memento dollar has no year but is struck in 1927. Give ebay a search on sold prices - I'm certain they are both good.
