Tandy DeskMate is a discontinued line of software consisting of an operating environment, and associated productivity software. Some versions of it include a bitmap graphics editor named Paint, which has a native .PNT file format.
The DeskMate versions named Personal DeskMate and Personal DeskMate 2 definitely used this format. It is not clear whether Professional DeskMate did. It is not clear whether there are versions for the Tandy Color Computer that did. As of DeskMate 3.00, Paint was no longer inclded, and instead there was a vector graphics editor named Draw.
Files begin with bytes
13 50 4e 54.