It is probably a stamping made after model A production was over. Ford made a fair number of blocks after model A production was complete for replacement engines and other equipment that used model A engines. These blocks had no engine number stamped on them. In fact I have a diamond block that has no engine number on it and the pad has NOT been ground off. I am posting a link that shows the diamond on a later block in the third or fourth post down. Does your block have the same diamond as shown in the upper righthand corner of the picture?
Rusty Nelson
https://www.fordbarn.com/forum/showt...lock&showall=1