I don't believe this is true. I have more (Husky) 9.3x57's than I can remember and all of them including those made in the twenties have both the receiver and barrel serial numbered. I just got one yesterday with ethe SN in the 453XX range and both are numbered.I also have in hand number 123CC and it too has both barrel & receiver numbered. Even my later model 146 series have the serial on the receiver under the front ring just ahead of the recoil lug, #206XX for example.Not strange when you consider that Husqvarna got it's start by making rifle barrels for the Swedish Crown. To them, the barrel was the important part. Occasionally you see an older muzzle loader barrel that has been reworked and put on a rolling block action. In fact, all of the modern sporting rifles (model 46 on) up till 1968 had the serial number on the barrel. The 1900 action guns made after 1968 were the first sporting rifles to have the serial number on the receiver for Husqvarna.
But, perhaps you meant ONLY on the receiver?
My later model 46's have the knurled ring between the receiver ring and rear sight band.
Woodbeef, these would not have stayed at the shop had it been me, unless of course the propietor thought too highly of them ($$$).