I thought patents expired a max of 15 years after publication date. Why does it seem like this patent still has until US Copyright Law expires (75 years)?
In reference to the patent: US2717437
A US patent issued in 1955 had an expiration of 17 years after issuance. US copyright expiration has nothing to do with patent expiration.
Longer answer: The 17-year rule was changed for utility patent applications filed after June 8, 1995, at which point the patent term became "20 years after filing". More variations and details can be found at 35 USC § 154 and MPEP § 2701.