Technical 300 HP 350 Casting date confusion

I have a motor I pulled out of a 69 Impala. The engine suffix is HN which shows it go be a 300 HP 350. The serial number is 19L044219 which shows it to be a 1969. Heres where the confusion starts. There is no date cast in to the usual place on the rear of the block or anywhere else on the engine in the usual format. On the right side of the block the numbers 9 3 and 7 are cast. See pic below. Is this actually a casting date in another format? Was hoping someone can shed some light on this.

 

never seen that....neat! Looks almost like a Mopar casting date

 

Wow, I stumped the squirrel! I thought you would have the definitive answer!

 

There's a whole bunch of stuff I don't know about!

but you can see what the assembly date is, on the other number stamped on the block. The four digits just before the HN are the month and day

 

They are VO312

 

March 12th 1969 does not seem to have anything to do with those cast numbers.

 

Possibly Canadian, does the prefix on the stamped I.D. start with MC? if so it was made in the McKinnon(spelling) Canadian plant

 

Are you going to build it or shop it around ? My casting books are at my man cave.......