First was the PT300. Based on the contemporary HT220; same basic boards, but with controls mounted off the board and on the case, and a bigger RF (and also audio) PA
There was later a PT400 (never saw one in person), and then the PT500, based on the MT500 portable, Again, same boards, just mounted inside that 'lunch-pail', and a bigger RF PA.
There was also a PX300; based on the MX-300 series.
The big bottom section on the bottom was the batterypack/power supply/battery charger.
The PT300 radios were (oddly, in my mind) built with 'positive ground'; woe to the technician that didn't know this to begin with, or forget it. He learned the hard way. Just don't ask me how I know.
Beside the handset you see in the article, there was also a regular hand microphone.
I know the radios were made in VHF-Low, and High. Never saw one, or even reference to one in UHF.
More info on Repeater Builder site:
http://www.repeater-builder.com/rbtip/mojoindex.html, & go almost to the bottom of the page.