Art and Net Worth

On one of the many documents we've been sorting through my mother estimated her and my father's net worth in 1995. The number she came up with is equivalent to about USD 1 million today (£350k at the time). But she estimated that an inherited artwork* they owned was worth £20k (USD 56k today). The next year the artwork sold at auction for... £750k (USD 2.1 million). Another letter from my father to his brother in 1954 stated that the art had been valued at USD 880 or around USD 8500 today.

*The art consisted of panels like on this cabinet, but not the cabinet itself: