741 Crankcase Question

[JTR249]

Why is it that almost every crankcase you see for sale through online sources has the incorrect number for a 741 crankcase? Everywhere I looked I see 85540--which is a 1935 number and not in the parts list for 41-45 Scouts. Are these all examples of people just selling something compatible that works or was there a parts number change? This first one is the one I bought for myself. The other two are examples of what is out there. Ziggy's is how I found out what they actually are after looking through every list and not seeing the numbers there.
Here are a few examples.
1935 Right Crankcase sold as 741.jpg

[T. Cotten]

You made me check my junk, JR!

85540, for what it's worth...

.....Cotten
PS: Perhaps they kept the same casting pattern, but changed the parts book number, for some update.