You should be aware that each BC-221 and the other heterodyne
frequency meters had its own individually plotted calibration book so
using one from another meter wasn't an accepted practise.

Still, if you don't have any calibration book anything is better than
nothing.

73,

Michael, W1RC

On Sat, 20 Dec 2008 22:49:15 -0500, "Tio Pedro"
There were some articles regarding BC-221 calibration
in the late 40s early 50s QSTs.