StacksVerified U.S. regulatory reference

43 CFR §3863.1-2

Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
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.