Though it may not be immediately recognizable, given the variations in Wehrmacht eagles, the tall, chopped off wings of the National Labor Service's long service eagle devices for 25 years (as here in gold) and in silver (fopr 18 years) were actually "diffrent" by regulation.
Of course, no Wehrmacht gold eagle could be worn alone, since those were always in pairs of 2 gold = 25 years or a gold and silver = 12 years.
National Labor Service calculation of HOW 112, 18, and 25 years of service could have been earned remain undocumented. Presumably, like the other Nazi organizations, earlier service in other Party groups was rolled into aan accumulated total.
Likewise, there seems to have been considerable confusion at all levels about which R.A.D. long services were to have been worn, when. Atbout the time the ephemeral 1940 shovel devices (see Miscellaneous Device: Shovel & wheatsheaves), TWO long service awards were worn together, like the Wehrmacht pairs. And that seems to have been the norm after 1940. But SINGLE 18s and 25s seem to have been worn BEFORE 1940, again suggesting a compilation of all forms of earlier service into a final "total."
In many cases, military outfitters simply used standard Wehrmacht long service eagles on ribbons, so it is not always possible to say what one means. Even on full size medal bars, where the 18 and 25 years R.A.D. deeagles were SUPPOSED to have been embroidered like the Polizei ones--Wehrmacht metal eagles were often used instead.