[78-L] Matrix MR-443-2 Pee Wee Hunt 'Basin Street Blues'

[78records at cdbpdx.com]

Greetings.  I have Pee Wee Hunt's fine version of 'Basin Street Blues' on 2 records, one is FM label, the other is Mirror label, both have the same matrix number MR443-2.  I'm trying to figure out what the MR stands for to connect the releationships between the orignal recorder label and these other two.

Any ideas?  I don't think its Mercury.

Thanks!  CDB