43 C.F.R. § 3863.1-2
Proof of improvements for patent.
Cite as 43 C.F.R. § 3863.1-2 (2026)
The proof of improvements must show their value to be not less than $500 and that they were made by the applicant for patent or his grantors. This proof should consist of the statement of two or more disinterested witnesses.