Here it is at Tower:
http://www2.towerhobbies.com/cgi-bin...1&I=LH3731&P=1
It just does not have a very stable reading when used to measure prop RPM. Jumps by +/-200 to +/-4000 RPM, yes 4000.
Calbrates just fine at 3600, solid as could be.

(spelling corrected!!!!!)