Air compressor help needed

[TomMull]

Edit 6/26: confirmed as Ingersoll Rand Type 30, model 253. Comments will still be appreciated as I will be having a look inside this week.
Edit 6/25: I have confirmed that it is an Ingersoll-Rand type 30. I think it is a model 253. Can anyone confirm or tell me how to confirm that?

I'm in need of advice on my "new" air compressor. It is a two stage 5 hp with an 80 gallon tank and it's from 1970 according to the previous owner.
It is extremely heavy so I removed the motor and pump so I can move it into the shop.
It runs and makes air and is extremely quiet. In addition to it's age, the only flaw is the lack of id tag. The previous owner apparently removed it.
Since it is off the tank right now I thought it would be a good time to refresh the pump but I have no idea how to identify it. I am reluctant to open it up without some assurance that I can get parts.
It looks like an Ingersoll Rand but certainly not sure. I'm also told that there were only a couple of companies actually making the pumps for various compressor companies back when this one was built. Here are some pictures. Any ideas or help will be appreciated.
Tom

 

[BlueMax]

Contact and send photos to! I'm sure they would recognize their own product..

https://company.ingersollrand.com/ircorp/en/contact.html

 

[TomMull]

Thanks for the reply, BlueMax. I'm not sure there is anyone there at IR old enough. I did find a rebuilder locally who can supply parts. There is also an IR outlet near Boston who might be able to help.
The outward appearance of the pumps is pretty much like the current models but I wonder how similar the inner components are. I think it will be possible to get parts from the numbers on the old ones once it is apart, but it would be good to be confident of that. It runs ok now in spite of age but has a slight oil leak and I'm sure would benefit from a go over.
Tom