Measure the distance that's there (easier than trying to measure to a GG down inside the camera body), and then use diopter calculations to back out the infinity-focus focal length. What you have is equivalent to a longer lens focused at infinity plus a 0.83 diopter -- take the distance you find, in meters, invert to get diopters, add the 0.83 for the closer focus, and convert back to meters. Done in 15 seconds if your calculator is in reach...
Polaroid was charging that for a camera that a) was calibrated to produce a passport-legal image size, b) would produce that passport photo in a couple minutes, c) would do it reliably, whenever called on, and d) used standard, easily obtained film. Their competition was stuff like long-roll portrait cameras that sold for that, made you wait until you'd shot 400 or more frames to get the images back, weren't even vaguely easy to use (focus with a tape measure, and better get the lighting right -- you won't know if there was a light problem for a week or more), and required buying film by the 20-roll case (that's 20 rolls of 100 feet each). A bargain if you had a small shop and wanted to add passport photos, especially since you could hand over the print in under two minutes.
Sonar focus? Those were supposed to operate at a fixed distance to give the correct image size. Does it just beep when the distance is right? Yeah, I've got an Autofocus 660 here with the sonar on it, sold for about $100 new, just before Spectra film came out. Mount a framing box on the tripod socket and it'd make a perfectly fine passport camera, except that you can't depend on the integral prints not to fade or discolor if you cut out a piece. My 350, however, could do that job with a portrait kit attached, and cost me $2 for the parts to repair it after I received it as a gift. Doesn't put 4 images on one print, but that's only necessary if people want multiple copies or you have a big volume of business...
