The SB-11A is a very sensitive alpha tube, comparable to the LND 7317 in some ways. It also seems sturdier and is certainly cheaper. The data sheet gives: 44-49 cps/uR/sec, so the CPM to uSv/h conversion ratio becomes 318 CPM/uSv/hr. SBT-11A Pinouts.
The kit came in the post a few days ago:
Out of the box there was a small modification that needed to be made to the PCB, some solder resist needed to be removed round holes drilled for an additional capacitor
The SBT-11A Russian Geiger counter tube
Assembling the kit using the supplied instructions was OK, however a lack of silkscreen and some of the package holes being the wrong spacing for the components made for an interesting assembly process (Also some of the assembly was performed on my Dremel Gas Soldering Iron).
Connecting up the Tube and turning it on illicit a serious of chirps from background radiation.
The Kit also came with a RT162 LCD screen, however I have not got round to wiring that up yet.