Yes, it isn't a body number though, it is a chassis number. On early cars (HK and early HT) they ran a dual letter. So a Pagewood vehicle constructed and assembled at Pagewood got a number like HK34567SS with one S above the other. First S belongs to the Body Assembly Plant. Second S belongs to the Vehicle Assembly Plant. If a body was constructed in one plant say Elizabeth and assembled in Pagewood it got an Elizabeth BODY plate and Pagewood VIN plate and the chassis looked like HK34567AS. Once the vehicles went to ADR plates they also got an ADR plate from the Body Assembly Plant. So for example a HG van assembled in the Dandenong plant got Elizabeth BODY and ADR plates, Elizabeth chassis number and Dandenong VIN Plate. They also lost the second letter off the end during HT (possibly at ADR plate introduction, maybe earlier).
This changed at HQ introduction where such a vehicle only got the BAP's BODY plate (and firewall/cowl number if applicable). I'm not sure how this affected HG commercials sold after HQ intrduction (or even if Dandenong, Perth or Pagewood built HG commercials after HQ introduction) but I assume they would have stayed as per the older scheme. Chassis numbers changed at this time to HQ style ie AHG prefix, LC did the same with ALC prefix.