From memory the 2 digit code is the production broadcast sheet code. Almost every part has a 2 digit code or the last 3 digits of teh part number listed on the broadcast sheet. There will be stickers on items with 2 digit codes or painted 2 digit codes on items like engine and box.

Here's one on the starter out of my HJ Premier:
starter.jpg

There is only one row of info as there was only 1 x wheel and only 1 x type of tyre on an XU3, and 92001123 is XU3 only. Should be 14x6 and I think the tyre was an FR78S14 4 P/R steel belted radial. Same tyre was standard on HZ Statesman. I did have a gut feeling at one stage, but couldn't prove or disprove it, that early XU3 HZ may have possibly used the same tyre placard as a HZ Statesman for this reason.
Remember that when HZ came around they had to have the separate tyre placard for Sandman as they were V8 only, which cut out a lot of tyre choices. HZ Statesman is the same, and the base tyres on the HZ Statesman are the same as what was base on an XU3.
However the fly in the ointment was the HZ Statesman had a few optional tyres and wheels that the HZ XU3 didn't: 14x6 wire spoke, 14x7 polycast and also ER70H14 6 P/R, E70-H14 4 P/R, F78S14 4 P/R white side walls plus a 195SR14 4 P/R on NZ delivered Devilles.

Can you take a photo of the placard?