Vintage Industrial Research Products Level-Matic Limiter. This is the only one I’ve seen in the UK. Even in the USA details of the Level-Matic are hard to find but it’s straightforward to use
The Level-Matic is a simple limiter with preset threshold & output controls. The simplest way to use it is to leave it set for unity gain and drive the input to whatever level of limiting you desire
It’s transformer balanced on the input & output and has a back-panel jack for stereo linking – if you could ever find another one!
Sounds awesome on drums – instant parallel drum smashing!
Subtle limiting also available…
Industrial Research Products also made the rather wonderful Transversal Equaliser, a unique equaliser with zero phase shift. Clearly they are into niche products
In excellent used condition. Tested & working 100%. Photos show the limiter for sale