These were imported into the US in the 60's, by an importer who 'sportered' them by bobbing the barrels, as well as on some, painting the metal gloss black.
Yours appears to be based upon an early Gew98 that didn't get modified to take the 323 diameter. If there is no 'S' on the barrel ahead of the receiver, then it still remains in 318, as you have discovered.
These usually run about $200, but I've seen one dealer locally drag one around practically begging to sell it at $150.
My advice- shoot it!!