Definitely a zerk tool. In the 50s some cars had as many as 45 grease zerks, and always one or two were plugged or damaged. If you didn't get them all, some owners would be right back with their car because they crawled underneath and checked them.
Which kind of raises the question of why they didn't just do the grease job while they were there.
I remember the introduction of the rubber boots that were sealed to the joint on both sides. A lot of tie rods and such had been using boots that just lapped over the joint on one side; when grease pushed out past the boot, you knew when you had put in enough grease. Shop foremen everywhere had to teach mechanics that you put in grease until the boot began to inflate,
and then stop. Lots of the fancy new boots got blown out while the learning was going on.
The Motor manual would list the locations of the grease points, but young shop rats (like me) quickly learned that it was faster just to look where there might possibly be a zerk fitting; once you found one, you could figure there would be more in that area. Like seeing a good tool on the yard sale table: one good tool hints at more.
All those skills, now useful only to people working on old machines - like putting a clean corner of the shop rag with which you were cleaning the zerk fittings over a fitting with a frozen ball, to allow more pressure from the grease gun to break it loose (the fact that you were probably driving fibers from the rag into the joint, too...well, no big deal).
