Fitting modern batteries to watches containing these Landeron movements can be a little tricky and will also depend on what type of case you have…so read on!
When this movement first appeared in the early 1960s, various literature showed a variety of ways to power the movement. In the left photograph below, one demonstration model had what appeared to be two battery compartments on the left hand side of the watch; in fact, only one was connected to the movement with the other solely for storage of a spare battery; it also had a display back. In the right photograph, an accumulator version of the Landeron 4750 based watch is being recharged using a conventional Ever Ready 1.5v U10 battery.
So if your Landeron-based electric watch looks anything like the two watches above, or if it has two crowns, one at 3 and one at 9, then your watch probably does not take removable batteries and you should refer to the accumulator page. If it doesn’t resemble these, then it originally took the WD-4 or the WD-5 disposable mercury batteries.
Couple these two batteries with at least three different cases designs and you have the following variations which should help you identify your battery needs:
#1. The is a small slotted threaded battery hatch on the back of the watch. These watches originally took the WD-4. Today you can use a standard silver oxide 389 battery; this has a smaller diameter and is thinner than the WD-4 so you should use a small non-conductive spacer for the modern 389 plus a small spring between the +ve terminal and the case back. Although a 386 appears to be a better fit, it is slightly too thick and causes the case back to flex inwards and touch the movement; this then shorts out the battery.
On my Midland watch, which uses a Landeron 4750, there is a slight variation on this arrangement, although the modern battery replacement described above is the same. On this watch, the battery hatch is neither slotted nor threaded but instead is a snap-on type. In addition, the battery compartment is constructed of clear plastic, so you can see part of the movement without removing the full case back. Finally, instead of having the 14 flats to open the case back (see picture below), it has more conventional slots for a Jaxa-type opening tool.
#2. There is a single large screw down case back, usually in stainless steel and usually with 14 flats around the periphery. It’s best to use a special tool (see below) to open these backs if you want to prevent damage! These watches originally took the WD-5; it was held on the inside of the case back by a ring and a circlip. Today you can use a standard silver oxide 389 battery but you will need a large non-conductive spacer to replace the ring and circlip.
#3. The watch has no removable back at all. These watches took the WD-5 and were clipped to the back of the movement. The battery can only be changed by removing the crystal, stem/crown and then withdrawing the movement. Today you can use a standard silver oxide 389 battery but you will need a large non-conductive spacer to clip to the back of the movement.
A few photos follow to demonstrate the variations and the solutions.
The photos below shows the first two variations of case back: with three watches having the small slotted hatch back and the other two having the large screw down back. The third photo shows a batch of Acetal spacers used to hold a modern 389 in those watches that originally had the WD-5 on the inside of the watch (variants #2 and #3). On the left is a case back with a WD-5 still clipped in the back of it; a loose WD-5 is also shown together with the ring and circlip. Finally, a rather useful tool for undoing the case backs.