This is the Realistic TRC-11, a 6 channel "no-frills" radio. Back in 1975, this radio cost $79, which was more (especially considering inflation) than you needed to buy a 40 channel mobile today. But radios cost more back then, so this price was in-line for the times. The TRC-11 featured a 6 channel lighted dial, a Volume, Squelch, a switchable Noise Limiter switch, a transmit/modulation indicator light, and a 6 conductor, wired-in microphone. The radio came standard with channel 11 crystals installed, leaving 5 open slots for the user to populate at their whim. Radio Shack also made a "sister" radio, the TRC-9a, which was virtually identical, except it was a 3 channel radio.
Because these radios were small and cheap (relatively speaking), they were fairly popular among the "strapped for cash" set. There were at least 3 TRC-11's and 2 TRC-9's in our local group. Performance was not that bad, all things considered. However, because the microphone was wired-in and utilized a 6 wire cord, it made upgrading to an amplified mic somewhat difficult. Modulation with the stock mike was not all that bad, but the mike was a clunky, cheesy feeling, awkward affair.
I actually still have one of these radios stuffed in one of my drawers. This radio belonged to my next-door neighbor "Spud", who got it (and a power supply) as a gift in 1975. I made him a dipole antenna out of extra aluminum elements from a parts antenna, and he was on the air. He lost interest in CB radio about a year or so later, and somehow I ended up with the radio.