I was looking through my Verlinden book on IDF Shermans and noted that the tank roofs and transmission covers don't seem to have casting numbers on them. Did any WW2 Shermans not have them, or did Israel manufacture Sherman replacement parts for themselves (which I assume unlikely) which didn't have them?

They were on ALL Shermans cast parts and represented the Part Numbers and Foundry that manufactured them. It never ceases to amaze me the places you can find them on certain Shermans.
Cheers

And ironically most kit makers choose not to mold them onto their Sherman kits.

Maybe photos aren't showing the right spot. Seem to be
here
and here and here ?

Jim

On the mid-war and later differential housings the markings were placed on the underside at the rear. Here is a photo of the underside of an M4A3E2 housing:

http://www.toadmanstankpictures.com/restore_38.jpg

On the turret, later modifications by the Israelis often obliterated or removed the markings.

All parts had markings when made, but don't forget that sometimes it was on the inside of the part.

KL