Price is for 1 NOS tube. This is dual system triode preamp tube with long plates, D-shaped getter. Made somewhere in the 1950s. Very rare with etched codes of Valvo plant in Hamburg - mC1 D6B - 1956 I guess.
Tested GOOD as follow:
Ia1 = 1.1 mA | S1 = 1.6 mA/V | Ri1 = 54.0 | μ1 = 86.4
Ia2 = 0.9 mA | S2 = 1.3 mA/V | Ri2 = 58.8 | μ2 = 76.4
Tested at: Uf = 12,6V | Ua = 250V | Ug1 = -2,0V
Good begins at: Ia = 0,7mA S = 1,2mA/V
Shipping will be Airmail registered with tracing number. Other shipping methods available on request.