Well the Schupa product (as well as any previous designs) was probably what is referred to as an electro-mechanical RCD. The modern US GFI is partially electronic in order to achieve the higher sensitivity of 6 mA.
To add more confusion, the first usable 30 mA RCD was designed by an Austrian, Gottfried Biegelmeier in the late 50s.
The oldest RCD I've seen myself is probably from 1955 and has a trip current of 1 A. It was used to protect a 3-phase socket in my great-grandparents' home in Germany. All other circuits in the house are TN-C (i.e. with a jumper between neutral and earth in each socket) but the 3ph socket was not, probably because the original electrician thought it would likely supply outdoor equipment (it's right next to the front door).
