The 300 designates the series. Models in the 300 series:
311 gas, wide front end, adjustable tread front & rear, general purpose model.
310 gas/LPG, wide front end, fixed tread front & rear. Utility model.
312 gas, narrow front end, daul or single front wheel, adjustable rear tread.
All models have "300" decals on the sheet metal. Model nr will be on the model/serial nr tag affixed to the dash.