"Air Counter-S" Japanese low cost sensitive Gamma rate meter- Any experiences?

It's a low cost unit that uses four PIN photo diodes as Gamma detectors. From what I've read, it is a fixed rage unit that goes from 0.00 -> 9.99 micro Sieverts. This is a really small amount of radiation. it is the same as 0 -> .000999 REM or RAD, or just shy of one millirad. Apparently developed for people away from Fukushima who want to know if trace contamination is around. No Geiger tube to wear out and runs on a single AA cell. I have one on the way just for fun. For about US $50 I'll have that much fun messing around with it. I saw a video where it was able to detect those old lantern mantles that were made with a small amount of Thorium in them. Anyway, just looking at it as a fun gizmo. Wondered if anyone else here had tried one. It is supposed to have faster response than the earlier model. Maybe the "-S" is for speed. Shaped like one of those tubular electrostatic dosimeters.