Engines that went out of production prior to 1978 may have been retroactively assigned a family type to expedite parts support (this is the case with the Perkins 4.107).
After a lawsuit from motorcycle manufacturer Phelon & Moore, Perkins dropped the Panther (and Python and Puma for the corresponding P3 and P4 models) and stuck to abbreviations from then on.
The 4 107T was used in UK Military electricity generating sets, the engines when in need an overhaul were rebuilt by a Kent based engineering works in Ramsgate, adjacent to the inner Harbour known as Walkers Marine (Marine Engineers) Ltd. Houchins of Ashford an MOD contractor would send an MOD inspector to verify dynamometer testing of power and smoke emissions both on start up and full power for one full hour (27 horsepower produced at 3000 rpm) being used near military front lines any excessive smoke whilst running would give the armies position away.
When the transport vessel "Atlantic conveyor" was sunk during the Falklands conflict a large quantity of these generating units were lost.
The engines when rebuilt could take up to four days of diligent running on the "Heenan and Froud" water dynamometer with great care given regarding application and duration of the load as minor tightening was not un-common, and a heavy seizure could result in disassembly and liner and piston replacement.