Here's a listing I found that suggests that the TMR4 was very similar to the TMR8 (4 channels vs 8 channels)
-JK
N4MW Regency Crystal Controlled Monitors List
TMR/TME
Original style monitors. TMR is the smaller package typically used mobile and TME the larger footprint "Executive" version. Both used identical circuitry and operated from 110 volts AC or 12 volts DC. The smaller TMR actually had a larger (4 inch) speaker than the TME (3 inch).
TME16HL Crystal Scanner, High, Low, and UHF Bands 16 Channels
TME16HLU Crystal Scanner, High, Low, and UHF Bands 16 Channels
TME8HL Crystal Scanner, Base or Mobile High and Low Bands 8 Channels
TME8HLU Crystal Scanner, High, Low, and UHF Bands 8 Channels
TMR12H Crystal Scanner, High Band Only 12 Channels
TMR1H Crystal Scanner, High Band Only Single Channel
TMR1L Crystal Scanner, Low Band Only Single Channel
TMR1U Crystal Scanner, UHF Band Only Single Channel
TMR4 Crystal Scanner, High Band Only 4 Channels
TMR8 Crystal Scanner, Base or Mobile High and Low Bands 8 Channels
TMR1A Crystal Scanner, "Flightscan" Base or mobile, for VHF AM aircraft range Single Channel
TMR8A Crystal Scanner, "Flightscan" Base or mobile, for VHF AM aircraft range 8 Channel
TME8A Crystal Scanner, "Flightscan" Base or mobile, for VHF AM aircraft range 8 Channel