the National Motorcycle Museum in Anamosa, Iowa (never even heard of it) went bankrupt, and is auctioning everything off in the Parham collection (most of the museum is his stuff)

a headlining piece in the art collection is the Von Dutch helmet, which shows the history of all the brands of Von Dutch’s bikes that he owned. Later the baby bottle nipple was added as a comment on the California helmet law.

John and Jill Parham, the founders of J&P Cycles, initially established the museum in Sturgis, where it lived the first 12 years of its life. 

In 2001, the couple moved the museum to Anamosa, which was also the home of J&P Cycles.

In 2017 John died, and the attendance since Covid dropped off so much they haven't been able to kept he museum going

https://www.rideapart.com/news/664103/national-motorcycle-museum-collection-auction

https://www.rideapart.com/news/640892/national-motorcycle-museum-closing-2023

https://nationalmcmuseum.org/2017/03/24/the-famous-engraved-helmet-of-von-dutch/