Not sure how, or even if, this can be adapted to this application, but in my younger days I was once given the job of producing a limited number of instrument panels for the prototype logging equipment we were constructing. These had to be stamped, not labeled as the final production pieces would end up. These were exposition units, they had to look like they were machine stamped.
I built a series of stamping fixtures using 1/8" stamps with 1/4" square shanks because that was the size lettering we needed, but this method could be adapted to any size stamp. These would slide over the panel and reach completely from one side to the other, with a slot the width of the stamps and a heavy plate underneath to back up the panel. Then I cut a series of spacers using 1/4" square keystock, which were shorter than the stamps. Enough to stack, side by side, the full width of the workpiece. The slot length was adjusted to fit the stack of spacers, with just enough clearance for the spacers to be removed and replaced by hand.
I would start with all spacers stacked in the slot. Using masking tape, I would write out the desired text using the spacers as guides. Then it was a simple matter of pulling out a spacer and replacing it with the desired letter. Because the entire length of the slot was filled with spacers, I could position the text anywhere within the span of the fixture.
The fixture would have to be reset for each line (often just a single word), but the end result looked very good after the plate was buffed.
Because the stamp was 'trapped' multiple strikes (if even necessary) were guaranteed to line up, and the shank was always perpendicular to the work.
It's the human element that makes the hand-stamped lettering difficult and sometimes unsightly. A good stamp can only make as good an impression than the hand that holds it.
