age must be written or printed and duly signed.

[Sidenote: Licensees.]

A licensee takes an interest less than or different from either of the
others. A license may be oral, written, or printed, and if written or
printed, must be duly signed.

[Sidenote: Must be Recorded.]

An assignment, grant, or conveyance of a patent will be void as against
any subsequent purchaser or mortgagee for a valuable consideration
without notice unless recorded in the Patent Office within three months
from the date thereof. If any such assignment, grant, or conveyance of
any patent shall be acknowledged before any notary public of the several
States or territories, or the District of Columbia, or any commissioner
of the United States Circuit Court, or before any secretary of legation,
or consular officer authorized to administer oaths or perform notarial
acts under Section 1750 of the Revised Statutes, the certificate of such
acknowledgment, under the hand and official seal of such notary or other
officer, shall be _prima facie_ evidence of the execution of such
assignment, grant, or conveyance.

No instrument will be recorded which does not, in the judgment of the
Commissioner, amount to an assignment, grant, mortgage, lien,
encumbrance, or license, or which does not affect the title of the
patent or invention to which it relates. Such instruments should
identify the patent by date and number; or, if the invention is
unpatented, the name of the inventor, the serial number, and date of the
application should be stated.

[Sidenote: Conditional Assignments.]

Assignments which are made conditional on the performance of certain
stipulations, as the conditional payment of money, if recorded in the
office are regarded as absolute assignments until cancelled with the
written consent of both parties, or by the decree of a competent court.
The office has no means for determining whether such conditions have
been filled. (_Rev. Stat., Sec. 4898._)

STATE LAWS ON SELLING PATENTS

In some States, laws have been passed by which attempts have been made
to regulate or prevent the sale of patent rights within their borders,
by imposing upon patentees or their agents certain State restrictions,
such as requiring the filing of copies of patents, making and filing
proofs, taking out licenses, procuring certificates, complying with
forms, or prescribing the terms of a note to be given for a patent.

While it has never been squarely brought before