Here's a typical engine/transmission VIN derivative gang holder, where one (or more) digits were manually changed for each job as it came down the engine dress line; each individual character die had a slot milled in one side, and the spring clip kept them from falling out:
Here's a typical air-powered frame VIN stamper - it clamped to the frame rail and stamped the top surface, normally in two places:
The body/cowl stamper was made by the same company (George T. Schmidt Co. in Chicago), but was a multi-segment indexing "egg-stamper" mounted on a swiveling bail like a spot-weld gun; the "egg" rolled one way for the cowl impression, the tool was re-positioned to the heater opening, and it rolled back the other way, and was then indexed one digit for the next job.
