I have looked through my early cars that I bought directly from a hobby shop
and have found that although what I said before is generally true, some of the
pins which look like they were supposed to have flat heads have a little bit
of a dimple in them. This appears to be more of an artifact of the molding
process rather than a design feature though.
The later pins actually had a very discernible dimple though, really a hole
in the center of the head. The spare Atlas truck pins in Atlas packages that I
got on eBay are this style.
Also, there does appear to have been some intermixing so other factors along
with the truck pins may have to be used to verify vintage.
Doug
