I saw the image on ebay also,and yes it certainly appears to be a Rotomo engine. I would be inclined to say model 1 because of it unusual number.
As blumbly says Victa used the early model 1 for industrial and Marine purposes before the introduction of the Tiger" engine they used for Marine Fitments. And yes they were coded with an X prefix and a very short run. Id be surprised to see them in high numbers.
The only other X prefix preceding the serial number im aware of other than the villiers X is the Hurricane. They started their serial numbers with an X also but ran into the thousands. BUT to my knowledge they were not fitted to Lawn Patrol mowers.
The fact its been redrilled tells me it was more than likely running the BMS 10 which was their own company designed and made engine. The VICTA 125' of the Rotomo Era was never fitted to this mower,or any other.
