OK Jonesy what you have there in the top picture left to right.
Model 5 Special Series 2.(Has edger slot cover.Well done)Wrong air cleaner on it.Which is the same as your blue one.That one has the right air cleaner.
Right one is Model 5 Special Series 1 with the correct wheels.All model 5's had those wheels on them.Models 5's range from 1957-1960.The engine with the number 94828 is a Model 2 Rotomo.The ignition plate and flywheel are from that same model.It should have the same muffler as your spare engine.As far as the spare engine goes,have a look at the engine number.If it is 10,000 and under it could be a Model 1 Rotomo engine.10,000 and over it would be another model 2 engine.I'd say it is a Model 2 only due to the fact there are more around than Model 1's.Model 1 Rotomo 1955-56 and model 2 Rotomo is 1956-57. I hope this helps.
