A one compartment decompression computer!
You have just described the perfect decompression computer for saturation diving! Only the slowest tissues drive the calculations.
Seriously, this meter probably "emulates" several of the faster tissue compartments that drive most of the recreational dives even today. It is really sort of clever, build a prototype and run a bunch of small chamber tests that, when averaged, drive the graphics design of the custom gauge face. No batteries or software upgrades required.
Considering that the alternative was to have one of these on the boat and dive with an umbilical, the SOS meter was not a bad option:
Here's a good article if anyone is interested.
SOS DCP: bendomatic or game changer? - Vintage Scuba Diving
How good or bad was the DCP? How come this device, often coined as delusional and dangerous by scientists, has tens of thousands safe dives to its credit?
vintagescubadiving.com