I'm reading the calibration section of the service manual for a spectrum
analyser, and that tells me to connect the IF output to a 'selective level
meter'. I've had a google and can find lots of (mostly antique) models, but
I can't seem to find anything that describes what one of these is.

Am I right in guessing it's essentially a narrowband AM receiver with a
power meter for the carrier? So a spectrum analyser with only one
horizontal point? Are they typically more accurate than a spectrum analyser
- or can I just use another analyser?

Thanks
Theo