The McRobert Instruments Laboratory (MIL) began producing its first audio instruments for Over Land Studio's (OLS) predecessor Studio7 in 1977, its first product being a passive mixer. Active circuits soon followed and by 1983 a number of over level processors had been designed and fabricated and used by OLS in live and studio recordings. MIL has produced transducers and signal manipulation devices in addition to the valve amplifiers and pre-amplifiers that it is most known for.

MIL devices are fabricated with the best materials available, as is usually the case in instances where production numbers are small or when a device is made to sustain severe use.

Not one MIL device has failed in service. Some of the units utilized by OLS have seen exceptionally severe service.

MIL ceased fabrication of complete devices in 2000 and now focuses on circuit module design and assembly work for other companies.