Offenhauser Intake

I have a Offenhauser 3 x 2 Nailhead intake. I believe it is off of a 322, but it has no casting number on it anywhere. i am looking for some help identifying it. It measures 8" center to center across the front bolt holes. I compared it against a 401 intake and I know it is smaller than that one, which measured 9".

 

That looks like the 322 ci manifold, #3413.

Offy made three different manifolds.
#3413 Buick '53-'56
#3557 Buick '57,'58,'59 LeSabre only
#5190 Buick 401, 425 ci

 

How do I know for sure?
Did it not have a casting number?

 

It looks like the smaller ports of the 322, but I can't tell for sure.
Yes, there should be a 4-digit # cast in it somewhere on an Offenhauser manifold.
I think Edelbrock stamped their numbers in.