ADDA FAN in the back means its a NV REV A?

All of the 4 bay units have a 92mm fan. The original NV (Rev A) also had a small noisy 40mm fan in the PSU panel in the bottom. In an attempt to quiet the unit, they went with a fanless power supply so the NV Rev B and NV+ only have a single 92mm fan on the back. I'm sure that over the lengthy production run of the NV/NV+ there have been several different brands of fans procured for these units. Like all manufacturers, they will send out for quotes to various suppliers of parts every year or so. If a qualified vendor has a lower price, they will change suppliers for the next period of time.

For example the fan in my 4 year old NV+ is manufactured by Y.S. Tech, but my spare fan (purchased in Jan) is manufactured by Crown. That is the same manufacturer of the fans in my two NVX units. I don't think the presence of a specific brand of fan indicates a particular version of an NAS model.