The "space in the head" of the early 1990's and back Phillips screwdrives are known as can keys. They were used to open Spam cans and the like, i.e. canned ham, corned beef, C-ration cans (some, not all, the P-38 canopener was used for most of those), and "Spam cans" of ammuntion as they used to come (i.e. either in a "Spam" can or an ammuntion can with lid, i.e. ".30 cal" can, narrow width, or ".50 cal" can, wide width). Here in Korea, or in the States at discount stores that sell canned food (i.e. Wal Mart with no grocery section, K-Mart, Dollar General Store, Family Dollar, etc.) they sell canned ham with the can key attached. Loose that key, you are screwed, UNLESS: 1. you have a Vic SAK with the described can key in the Phillips Screwdriver, OR, a pair of pliers to literally pry-off and away the metal strip that comes off as you use the pliers. I have used the can key on the Vic SAK, it works, but not as good as the key that is typically glued to the can's lid.
I bought a small Tinker in 1992, and lost it soon afterward. Had the can key in the Phillips screwdriver.
I also have a 1980's pre-pliers model Craftsman (basicly, has fish scaler instead of pliers, see 1985 Vic catalog, or see Felinevet's website with one for sale) that has a Phillips screwdriver with can key. When I get home in 5 days, I will make pics of it and post it for show and tell.
It seems the can key went out in the late 1990's, as I have bought some new-old-stock Vic SAK's from the Seoul Vic store in the Namdaemun market (i.e. Grand Prix with hook in lieu of flat headed screwdriver mounted on the bottom) that does not have the can key. None of the OHT's, GAK's, 2008 Soldier, etc. have the can key in the Phillips screwdriver.