Hot Rods 3-71 identification

I have these numbers stamped on the top of my 3-71 (pic attached). Is there any significance to them, or are they just numbers that the manufacturer used to identify the casting?
Back driver side - 4518DH
Front driver side - 18
Front p*** side - 6774

 

they probably meant something to whoever stamped them, but not to anyone else...

Is there a casting date on the bottom of the case? That's the only useful number I've found on my 6-71

 

Unless the picture is distorted, that looks like a 3-71.

 

Case and rotor length on a 3-71 is 7.482-inches, and the case has two ribs.


Case and rotor length on a 4-71 is 9.98-inches, and the case has three ribs.

 

I think this a photo posted by Squirrel some time ago for reference?

 

Looks like a 3-71 to me too?

 

I’d also have to say a 3-71 being it has 2 ribs.