Camelion alkaline plus LR1 or N size 1.5V battery.
The LR1 is a popular small 'N' type battery commonly used in clocks and alarms. It is also popular with anglers in the Fox M Carp Bite Alarm.
This LR1 'N' battery will likely be your best option for replacing the obsolete mercury battery of the same dimensions. If you need to replace a Mallory RM401, Duracell RM-401, IEC-MR1, NEDA 117M, 910M, Everready E401, E401N, E401 N, Energizer EP401, EP401E, NR1, R401, RP401 you will have little choice but to use this LR1 / N size battery.
Also known as LR01, MN9100, N, E90, 4001, KN, KN-2, AM5, 810, 910A.