t some point (still pre-World) they started making that area flat, a dead giveaway that it was not an original block.
I've seen very few of that version.
This post is worth even less than the previous one, but I've attempted in the past to figure out the rough timeframe for this one change detail, given up and failed.
If someone goes digging for that info, I'm not your guy LOL.
When that happened, there should have been an upsuffix (the end of the part number would change to reflect the physical change, like AD to AE, etc),
but there is a good chance it was not documented in a way to provide any visibility.
