Whilst looking on the bay for some Atlas #4 switches, I happened upon more than one seller who was listing as ATLAS HO #4 switches, when in fact, the product being pictured were SNAP Switches. Several were in the package, with the 1/3 curve piece standing out boldly. Others you can only tell by looking at the frog as they are markedly different. Obviously either certain sellers have no idea what the difference is between a SNAP, or #4, or #6 Atlas Switch, or they are just plain selling goose-poop to the unaware.
I think maybe the problem lies with the snap switches being real #4's while the seller may realize that most of us know the non-snap #4's are really #4.5's and generally better for our railroads.
IMHO, Atlas Snap Switches are tighter than a true #4. I've measured them at about a 3.3, others' estimates on-line are in that same range.
Not a problem for me since I don't use anything less than a #6 anyway, #4 are too tight, and 4.5 too tight also.
Some times those tight switches comes in handy for small ISLs. The only way I could get what I wanted was to use small switches. Those are 9" snap switches.