TOPIC: Tee Nee I.D. help please

Found this tag easily enough but what other numbers should I be looking for, and where should I expect to find them?
Is this possibly 1958-59' OB-40-A or a OB-50-A ?

and if it is... what are the differences physically between the OB-40-A and OB-50-A ?

Thanks in advance - Bart

Here are some scans from a 59 brochure, I believe you are correct that it's a 58-9 OB40A. Not sure what the relationship was between Aluma craft and Tee Nee, they were obviously both from Youngstown. The only differences I see are the wheels, fenders, winch stand and carrying capacity. As far as I am aware, the only numbers are the serial number, which you have already found.
Cheers Bill