P40 synchronized guns

Dear All,
I'm looking for a bit of information about P40 versions equipped with nose mounted 0.50 guns.
According to official guidelines, a notice in the cockpit had to be placed, indicating the min - max engine rpm range for safely firing through the propeller disc.
I'm looking for these two numbers or for an image of the cockpit note stating the engine speed range good for synchronized firing.

Could someone kindly help me?
Thanks in advance

8 years later....
A nameplate similar to this was on cockpit upper longeron, left hand side, just forward the throttle quadrant, the min-max rpm was 1000 & 2500rpm

Better late than never - at least that's what Custer would have said.