The stamp typically determines who manufactured the battery. Some
batteries sold as true 901
batteries are actually RN batteries. But the 2 are interchangeable.
Off the top of my head.. if the whole DSE901 assembled = 118.8mm its a DSE901, if its 119.5mm its a RN.
RNs are rated at 200mah, DSE are rated at 180mah
both operate at a voltage of 3.7v .. give or take depending on charge.
Ussually though.. the are stamped with SHO or SLB... or nothing at all.
NO and SY are new to me.