Here's a link to a thread for assisting in determining when a W49 was made. I still haven't got around to getting the pictures taken.
The tang stamp charts are OK, but they are incomplete and the dates are somewhat off, IMO. Some of the stamps are for folders only, some on FBs only, some of stamps were used on folders at one time and on FBs at a different time.
Pictures are very useful in determining about when the L66s were made. Overall pics and of the stamps on the knives.