Welcome back David,
This is your father’s “railway pass” ID document that verified him as a recipient of the Virtuti Militari. It essentially states that he has been decorated with the VM by the government body organized for this purpose. Veterans decorated with Poland’s highest military order were granted several perks by the government, one of which was free rail travel. In 1933 it was decided that such a document was necessary as a form of identification for this purpose and others.
Do you have the matching cross, and perhaps the formal award diploma?