[cctalk] IBM PC/XT and NEC "gold" tam

I have an xt mobo and some portion is populated w/NEC 4116 or 4164 chips (but 4116s were specific to the 5150, no? It's not in front of me). There are a bunch on the board, not sure if it's all the ram. Was this typical (I'm sure that wasn't the case). Is this an example of an early 5160? Why did they goldnplate the covers?