It's got 5" front wheels like my Tractor 8. The Tractor 11's had a 6" front wheel. Something else I noticed is that your frame doesn't have the 'running boards' behind the pedals. These were on the 11's but not on the 8's, I think. Photos below of two of my Tractor 11 donors showing this. In short it appears to be a Tractor 8 frame. However, the engine is 11HP (400cc). Possibly it has been re- engined? Might be interesting to get the model,type and code off the engine one day.
All this is just a distraction really. It doesn't really matter. The only way it's of any importance is that you need a 6" rear wheel and not the 8". I'll have a dig around. Not sure if I have one as I haven't parted out any Tractor 8's
