Just pulled 4 period shovels out of the shed. I am pretty well convinced the number refers to the shape/size of the blade and has nothing to do with a particular vehicle application or handle bends.
Here are 4 shovels.
1. Conventional "straight" 30 degree shank Stamped #2. The handle would stick out if fitted to a jeep.
2. "Jeep style" curved extreme 45 degree angle shank Stamped #2. Note blade is same as #1.
3 Conventional shank, angle same as #1, coal/sand/snow shovel large blade Stamped #3
4. Large conventional shank, angle same as #1, British "T" handle Stamped #5
