Seven years after Copper Industries (Houston, TX) purchased Weller Electric Manufacturing from Carl Weller they published their November 1977 Product Catalog #600.
The Weller WTCP and WTCPL were discontinued in 1976, except for some late military orders. I repaired a US Navy surplus WTCP station with a 1977 ink stamp inside TCP-1 iron. The 1977 catalog shows the the WTCPN model (replacing the WTCPL model). This model would be in production for 5 years (1981), when it would replaced with the WTCP series model (same form factor) that featured many changes.
* New TC-201 soldering iron. Plastic molded blue handle, black heater insulator, plug-in heater (EC-234), updated 3-pin iron connector (with twist lock).
* Power illuminated rocker switch changed from Carling TLG-Series Mid-Sized Tippette snap-in rocker switch https://www.carlingtech.com/sites/default/files/documents/TLG-Series_Details_%26_COS.pdf
to the Carling LRA-Series Curvette illuminated rocker switch. https://www.carlingtech.com/sites/default/files/documents/LRA-Series_Details_%26_COS_0.pdf