Technical Piston Identification

I picked these up today but I am having trouble finding info on what they fit. They are Elgin and the box says EP 100 STD but the piston itself is marked ES 101. The top if the pistons has a slight crown to it. Ford flathead? Whatever they are I don't need them so once I know what they fit I will list them along with a set of 6 I picked up for 1934 to 1943 Dodge, Chrysler and Desoto.

Thanks

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The pic.

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what diameter are they?

 

3.3"

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likely 3-5/16" bore?

 

Look like 4 ringer flathead pistons.