Actually, it *is* serviceable. You can replace the charcoal inside with new activated charcoal from a pet store (for aquariums). In doing some research a couple years ago I found that the older canisters like that are fairly rare and pricey on eBay. Folks restoring mid-70's muscle cars pay top dollar for them. Of course, it doesn't hurt to clean it up and re-install it on the Jeep. It serves a useful purpose in recovering gas vapors evaporating from the tank and it doesn't rob engine performance in any way.
Here's my write-up on rebuilding mine: http://jeep.smallcraft.net/canister/