Yes, it would appear to be a CB microphone with the 4-pin plug removed and a wee box with a jack socket fitted instead. Maybe it's a "power mike" with a preamp built in - if you want to make such a thing, I recommend picking up a copy of the ARRL Handbook, RSGB Handbook or "Technical Topics" by Pat Hawker G3VA (a very clever man who designed incredibly compact radio equipment during the Second World War, and referred to his "suitcase set" designs in veiled tones in his Technical Topics column in Radcom for years ;-) ).
I could stick a quarter inch jack socket on some Tait PMR microphones. Guaranteed to have been used and abused, and subjected to the sort of battering they can only get in a council workman's Transit van. Mine's a pint, thanks.