A little hard to read upside-down.
Couldn't find anything using RTS-5448 or 7M58. That last could be a date code.
I was able to find some info using RTS-544.
https://worldradiohistory.com/hd2/ID...-Page-0084.pdf
Looks like it is the B-01 variation of the RTS-544 chassis.
RTS-544Y would have a UHF tuner also.