Do not confuse with 388 button cell, also numbered 221.
Basically this battery is a stack of 15 × LR54 with a metal "pip" contact plate at each end and a casing to hold it all together.
15F15, 15LR54, 221, 505, 75, 505E/B, A221, B155, BA 333/U, BL-MV15, BLR155, M505, MV15, MV15E, NR75, W15, Y15, Y-15,
not to scale.
Height × Width × Length.
|Chemical Composition.||Nominal Voltage.|
|505.||50.9 mm × 15.9 mm × 15.1 mm|
Although some are round:
50.9 mm high × 15.9 mm diameter
Contacts: Raised areas either end for Positive and Negative.
|Carbon Zinc||22.5 volts.|