Technical Identify these Flathead pistons.

To the Flathead guys.
Take a look at these pistons for me and weigh in on what you all think they are.
Motor is a stock bore Ford 1946 59AB. Took the heads off (see Photo) and saw "STD" stamped into all the piston tops. Also no center "dimple" as I see on quite a few Ford flathead pistons.
Tops are domed and have concentric circles on them.
Question. Are these stock slugs, factory replacements or aftermarket?

 

I would say replacements stock bore , stock compression . Never seen a stock piston marked "STD" sexually transmitted disease ?

 

Closer up.

 

Stock bore replacement, looks like the block is sleeved back to stock. Looks like a good flathead, put the heads back on and run it.

 

Yea!! I don't think the piston cares whats stamped on it!! The sweet sound of a Flathead!! Pete

 

You're right--back then they would have stamped them "VD"

 

Why not measure the bore?

 

Like the original post and the piston tops say, the bore is standard.
Tough to figure out as suggested in post 2 , why would someone replace a full set of pistons with standard bore, and stay with stock compression?
Anybody have personal photos of bone stock Ford factory 239 piston tops? ( harder to find on the internet than it sounds)
Are stockers "domed"?
Or anybody know who manufactured the "STD" pistons?

 

Looks like stock fords to me. "Std" is definitely standard bore. And I'm not sure I would call it a domed piston but stockers do have a slight dome in them.

N.O.S. .030 over Ford piston.


I don't know if you can see it but it's stamped N +.030. Also note, no dimple, and the machine grooves.

 

When I opened up my 8CM engine, those Pistons had STD stamped on them. Why somebody did this, who knows but made me happy.

 

Thanks Shoop.
Thanks AVater.