That’s not possible. The chip used in that model was limited to 16GB. I worked in IT at that time and DB admins begging me to get them a 15” at that time with 32GB of RAM. I told them the chip from Intel was the limiting factor. When Apple updated a year or two ago, they moved to the next version of the chip which allowed 32GB. So yeah, 32GB in 2015 was not possible.
Interesting. Any guesses why anyone would have a sealed one, given that anyone could assume it would depreciate relatively quickly? (It's not really a "hold" commodity.)
Also if it's not too personal, roughly how much did you pay?
The going rate for them when I picked it up was around 1,800 - 2500. Check past/completed listings for sealed 2015 macbook pros. The higher end ones are rare, but they show up occasionally.