I did a search but did not get a hit. Can you use a CR-1/3N lithium battery in the OM-2 and OM-4? The manual only mentions 2x SR44 silver oxide batteries. But the OM-3 manual does specify a CR-1/3N lithium as an alternate battery to the 2x SR44 silver oxide batteries. Never mind, I did a wider search and found my answer. Silver oxide for the OM-2 and 4.