Technical Advice on Original Edelbrock Slingshot

Hey guys
Wanted to post some pics of a Edelbrock Slingshot I just picked up. Just curious as it's an original one but can only find stamping numbers that say 263. Is this correct? Any advice about the year it is or numbers would be appreciated. Thank you

 

New ones have a boss cast into it where the made in USA tag is .. You'd probably be able to tell if it were ground off ...

That one looks old based on pics I'd bet some money it was legit

 

I'm pretty sure it's the real deal just trying to shed some light on the numbers I see.

 

Any other thoughts guys?

 

Probably a serial #

 

From what I have heard from flathead guru, the late Bruce Dahl, Vic Edelbrock numbered all of his slingshot intakes on the reverse side starting at 100. The slingshot was Edelbrock's first intake that he cast and was the beginning of a multi million dollar company.