This is Rollei RPX 400 developed in Rodinal.
It appears to be a decent ISO 400 B&W film, with reasonably fine grain.
It comes in nice little plastic canisters.
As you can see, “we” were very busy here.
(If you’ve never tried to focus a large MF camera and hand rocks to your child, you really should…especially at f/2.8)
…Just be careful not to drop either on him or her.