BB V8 Rear Main Seal ID

[LSS&B]

I received this big block V8 rear main seal retainer with narrow side seals in a box of parts years ago.
Has a PDDC logo and last 5 of casting number looks like 21389.
Is this from a later factory big block?
Or is it something MP produced after big block V8 went out of production?
Thanks for your help!

 

[69Bee]

1821389

 

[boboh1]

Here is a picture of mine from my 1969 383. I think my side seal channels were larger

 

[rickseeman]

No, it's earlier. I don't know what that notch is. I say it's not BBM.

 

[69Bee]

No, it's earlier. I don't know what that notch is. I say it's not BBM

Here is a pic of the 1961 parts manual...

As far as the notches, some one could have done that on a mill for some reason.