This is the typical WF8955AN Power Distribution Panel with the WF8955 Converter/charger unit installed in the bottom compartment where you hear the fan running...

The 120VAC Circuit Breakers are located on the left and the 12VDC FUSES including the two REVERSE POLARITY Fuses are located on the right side.
The circuit breaker labeled 'CONV' would be the 120VAC breaker for the WF8955 Converter unit in the bottom compartment.
This is the WF8955 Converter unit installed in the bottom compartment of the WF8900 series power distribution panel. There are no 120VAC circuit breakers shown installed in this google image photo.

The INVERTER unit you have referred to would be a custom install item added to the trailer to provide 120VAC when you do not have access to shore power. The INVERTER units are usually installed in a weather tight compartment closest to the battery bank.
Just my observations
Roy Ken