The Vintage Collective - No more battery problems for the Pentax Spotmatic SP The Maxell 394 silver oxide battery os a replacement for the discountinued PX-400 (RM400R) battery 🔋 🎞 Maxell SR936SW (
The trouble with mercury batteries (and what to do) – - Daniel J. Schneider
Amazon.com: Battery, WEIN Cell PX400 Replacement Box of 12 : Health & Household