Date Code Question

How do you read the date code on a big block water pump housing? I have housing number 2780987 for a 67 car. The casting date is 12-16.

Thanks
Dan.

Not sure but it could be 12 1 6 or December 1st 1966 which would be correct for 1967 model year.

Or 121st day of '66? May 01. But doubtful if the hyphen is there.

There is a - between the 12 and the 16. So I wouldn't think it to mean 121st day?

Thanks.
Dan.