Inspector reported a main wheel axle nut came off during aircraft towing. The wrong axle nut was installed; allowing the main wheel assembly to come off; damaging the threads and axle.

Narrative

I did not witness this; I was told after it happened: '#1 tire came loose; while towing airplane from bay to blast fence. Loud popping sound was observed and upon investigation; found #1 tire cockeyed. Removed hubcap and found axle nut completely removed from axle; possible thread damage on axle and axle nut; outboard bearing inboard and outboard retainer and seal damaged; axle nut locking bolt sheared; brake assembly damaged.' 'They observed that the incorrect axle nut may have been possibly installed. This axle was modified and requires the reworked axle nut assembly (yellow colored) but white axle nut was installed and appears to have much play possibly leading to this incident occurring.'I was called to give ok to install the #1; #2; #4 and #6 wheel assemblies of the left Main Landing Gear. I gave them the ok to install and went on other job calls. When the tire installations were completed; I returned to the left Main Landing Gear to verify that all four tires were installed. I did not see the nut installation since the hubcaps; clamps and lock wire were installed. I believe more training is required on how to identify the proper hardware to use on the Main Landing Gear.