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3
votes
2answers
50 views

How can I determine the date of a patent sale?

My great grandmother Lizzie M. Adams sold her patent (number 680,106) to C. H. Munson in the early 1900s, I think. I have a newspaper article of the sale but no date.
2
votes
3answers
100 views

How big is the US patent market in Virtual Reality patents?

I'm trying to work out how many virtual reality patents are assigned each year, and how the size of the market has changed. I also want to work out how many patents are reassigned each year, and how ...
0
votes
1answer
119 views

Why are the assignors of a patent not necessarily identical with previous assignees?

When I researched the assignment history of a patent I found one assignment (from assignor A to assignee B) and a later assignment (from assignor B and C to assignee D). Where does C come from?