I'm sure others are will be better able to assist in dating the pieces. The do appear to be fukagawa pieces. I had to chuckle a little though... they're labeled "futaku"... kind of like "just a usual ol swamp"... someone obviously had a bit of a sense of humor for the intended foreigner buyer.

There are many marks similar to Fukagawa (all Mt Fugi). The Made In Japan likely indicates 1940's until the Occupation after the war. Although we didn't import anything from Japan 1942 -1948, things were still being manufactured and could have been purchased and brought to the US at some point in time with the Made in Japan in the back stamp. However, anything manufactured 1945 - 1952 would have said Occupied Japan whether purchased in Japan or imported. After 1952, we're back to Made in Japan, again.
Not much help but it's prior to 1945 or after 1952. Probably not much earlier as the words were usually not Made In Japan, just Japan or Nippon. You can do some research on your grandparents (such as ages, were they ever in Japan, etc. A lot of men brought back sets after the Occupation).

Yes, I think they're worth bothering to sell if you want to find them a better place to be. You'll probably get more money if you sell them as single sets or two or four. I don't think they are really old and probably not going to have much appeal as a set for eleven. Test the water with one and see what kind of response you get.

I forgot to say, I'm in Norway, and so where my grandparents. I have no idea how they got a hold of these, they didn't travel to Asia as far as I know (my father is also dead, so my information is very limited). But they where quite rich, and had a lot of rich friends, so it might have been a gift from someone a bit more adventurous.

Thanks for your help, I'll put one of them on eBay, if that isn't a big success I'll just sell the rest of them on a Norwegian site, mostly for giving them a loving home =)