Triumph Repair: differential, prefixes, spitfire

Question
The number stamped on my 1979 Spitfire is 88311425. There are no prefixes.
How can I find out what these numbers mean in relation to what gears are
supposed to be inside.

Answer
Hi Mack,
Never seen a differential without a prefix. "FH" is US and "FR" is non US version. US ver. is 3.89 : 1 and non US is 3.63 : 1.
As far as what gear parts numbers all you need to do is open it up as most have the part number stamped or etched on them.
Howard