What conditions must be met for a later buyer to have good title of a patent?

For a later buyer to acquire good title to a patent, it is essential that they are unaware of the prior sale and that the first buyer did not record the assignment. This principle is rooted in the "first to file" and recording requirements under patent law. In situations where an assignment has not been recorded, a subsequent buyer who is completely unaware of the prior transaction typically has the opportunity to secure a good title to the patent.

The rationale is based on the premise that the US patent system operates under a "first to invent" rule, but when it comes to assignments, the recording acts put forth the necessity for recording as soon as possible to put potential buyers on notice. If the first buyer did not record their assignment and the second buyer has no knowledge of it, the second buyer can claim they have acquired the rights validly. This encourages transparency in transactions and protects good-faith purchasers.

Other options present conditions that are not necessary, such as requiring the first buyer to record within a specific timeframe or the knowledge of the second buyer pertaining to the original buyer, which do not accurately reflect the concept of good title in situations where the assignment was not recorded.