I used these professional Simpson VU meters in the '70s and '80s to monitor the stereo outputs of pro audio and recording equipment.
They are marked L74150 on the rear and measure 3.25” x 3.25”. Fitted with shielded cables attached to balanced female 3-pin XLR connectors. The resistors were placed between the terminals to better match the line outputs of the equipment being monitored.
The pointers still float free and worked perfectly the last time they were used.