CRT Question - Old Calculator

I beleive, strictly, the German diode is an OY3, not a 0Y3. Old European semiconductors used the smae letters as the vlave code. The 'O' (not zero) for the ehater voltage meant semicondcutor device. A is a signal diode (so OA81, etc), C is a triode -> transsitor (so OC71 germanium transsitor) and Y is a power diode/rectifier. Actually, those letters -- almost -- carry on to today. The first letter was reassigned ot be A for germanium and B for silicon. So an AA119 is a germanium signal diode. C is still trasnistor (think of AC128, a germanium transistor and BC108, a silicon transistor). D, originally power triode is sometimes used for power transsitor (AD161, BD131, etc) .F, origianlyl a pentode, then became an RF transistor (which makes sense, both are high frequency amplfiiers). So AF117, BF259, etc.