PIcked up at a flea market for 14 bucks. Help iding what exactly it is.

[edteach]

I picked this up at a flea market. Its a Sheaffer white dot but what one is it? Why does the cap not have Sheaffer written on it? After the pictures were taken its soaking in hot water with some dish soap to clean the old ink out. How do I test this pen to make sure its still working and how hard is it to rebuild it if its not working right? Thanks.