I must agree. Even though I have both and sat looking at them, over and over, and kept them side by side in my book...

One looks like the HS machine was hotter and made a deeper impression.

The machine has a control for the amount of pressure applied as well. Since they don't want to make a blob and squash the chip, it is adjusted for a nice impression.

Either more heat or more pressure, will make the larger appearing hot stamo, from the same die and design.

Note: I still saved both of mine, but I think they are just two different batches of the same chip.