
I added a fourth and fifth No199 utility knife to my collection recently, and didn’t expect any surprises, but I got one when I opened them up to remove the dull and rusted blades. Inside, one had a single Stanley No1992 and several General No852, the other had several Millers Falls No3325.

The one with the MF blades was
more heavily-constructed than the one with the General blades!

This led me to open up the NOS examples, which were stocked with
unmarked blades, sharing the size and angle of the MF and General blades, but with two notches (like the Stanley, but not sharing the length or more acute angle of it) instead of three. Hmmm. I had hoped to use the blades to establish whether the heavy knife was older or newer, but the blades may not help. Neither NOS examples, nor another earlier acuisition shared the heavy construction.
I’m favoring the “heavy is older” theory for now, but will have to see if Stanley utility knives show a similar internal redesign.