This is the Midland 13-428, 3 channel 100 mW walkie-talkie.   Features included: a Volume control, a Push To Talk (PTT) switch, a "Call Signal" switch which, when activated, would send a beep tone when transmitting.  Rounding out the list of features was a 3+ foot telescopic antenna, and an earphone and external power supply jacks.  The receiver was a super heterodyne, and was fairly sensitive especially compared to the super regenerative, Channel 14, "kiddie" walkie-talkies that most of us started out with.  This radio came equipped from the factory with Channel 11 installed (Soldered in) in the "A" position, with sockets to add up to 2 additional channels.  Range on this radio was usually between 1/2 and 1 mile, depending on your location.  Hiking up to a tall hill could greatly increase range.  I received this radio as a birthday gift in early 1973 and used it extensively until getting the Midland 13-700, 1 watt walkie-talkie on the following Christmas.  After that, the 13-428 was relegated to secondary status, and just for kicks and grins, I installed a crystal for the local fire dispatch frequency (33.700), which used the same I.F frequency (455 Khz) and surprisingly it worked!  I had to realign the radio for best sensitivity, and it was actually slope detecting the FM transmitters, but I could now easily monitor local fire calls, and the Midland was much more sensitive than the tunable radio I had been using.  Some years later, also for the fun of it, I tried 49 Mhz crystals in it and they worked as well!  It wasn't nearly as sensitive as the Lafayette HA-240, but I was surprised that it worked at all. This radio has seen a great deal of accidents and abuse (drops) in its life, and over 30 years later, it really shows it. The antenna is not the original, it's from the 13-700 1 watt, which unfortunately did not fair the years as well as this radio.  A bit ironic, as the 13-700 was a more physically rugged unit.