When I bought my LEAF, the dealer (not a Nissan dealer) told me that they sometimes buy the used cards from eBay or wherever, and then slip the Nissan dealer a $50 or so to reprogram it to the LEAF they're trying to sell.
Do the map updates go into the second SD card slot, or do they replace the main card? If they replace the main card, then there's probably some (perhaps simple?) mapping between the three values SET/SNO/NAVI-1 and the three values that you need to give when buying the updated maps.
2012 LEAF SL in Cayenne Red
40 mile R/T commute in Chicagoland
Leaf Spy Lite (June 2015, 22513 miles): AHr = 56.86, SOH = 86%, 393.13V, Hx = 73.55%, 924 L1/L2s, min/avg/max = 4.080 4.097 4.109 (29mV)