The gear box has a shift lever that puts the machine in low gear for metal cutting and there are step pulleys to change the speed from low to high in low gear or high gear so you can cut at up to 8(i think) different speeds, four for metal and four for wood.
sort of....
It's got a 4-step pulley that mates to a 4-step pulley on the gearbox for metal cutting operations and uses a short v-belt for (4) different speed ranges. The gearbox itself provides roughly a 30:1 gear reduction (if not mistaken) to the lower band saw wheel shaft internal spur gear. I've owned and fully restored several of them.
When you cut wood, you put a longer v-belt on the motor pulley and it mates to a larger 8" pulley on the lower band saw wheel shaft for (1) speed operation.
As nine4gmc has stated, the shift lever on the gearbox simply disengages the internal gears from the lower band saw wheel shaft spur gear. You engage when cutting metal, and disengage when cutting wood.
You can hop on over to
www.owwm.org or
www.vintagemachinery.org to see many more pictures, and also download a plethora of O&M manuals and parts lists for these vintage machines.
This wood/metal band saw is "ok" for light duty metal cutting work at best but is not set up to utilize a blade coolant system as is conventionally found on horizontal metal cutting band saws. Nor does this band saw have a vice to secure the work while being cut. This is a major disadvantage over a horizontal band saw or chop saw.
If your sole purpose were to use it for metal cutting operations, I'd pass unless you require unique shapes in heavy gauge sheet metal work.