Help me id a mag pump

[Samper]

I bought a used mag pump from a guy and the plate that covers the impeller is broken. There are no stickers or anything on the pump so I don't know what size exactly it is. Are all the covers the same? Is there a way to tell what size it is if not?
The pump looks like this one. I don't think it's made for salt water though since the screws are beginning to show signs of rust on em.

[The R/C Man]

The MAG 3-7 have a different housing so that is at least a 9 or better. I would use the measurements of the pump and the rating on the case and compare that to the website for conformation.... Good Luck!