Did you have to use an ink pad, or was the ink somehow integrated into the device?
The price guns I remember were all metal, like the rotary stamp you posted. All I could find on the Internet were plastic models, and even they looked like antiques. I keep forgetting I’m that old.
In "resting" position, the numbers you set on the dials were flush against the pad getting inked. When you wanted to mark something, you pushed down on the handle and the numbers rotated 180 degrees (hence a rotary) to face the bottom and mark the item.
My career as a grocery clerk (a summer job in the late 60's) ended before the price labels arrived.