For anyone interested in History......
The vacuum check idea goes back at least to 1993. Howard Hall needed a way to verify integrity of the IMAX Salido housing containing 3D camera equipment worth $2,500,000. The vacuum system was devised, and indeed resulted in a safe dry camera every time. He and Bob Cranston have since employed the vacuum checker on every underwater housing.
2003: Gates designed and built 2 custom F900 housings for Bob and Howard which included a vacuum check port. It was our introduction to the system. Shortly thereafter it became part of our standard factory test. It allowed quick identification of leaks, but more importantly it revealed a way to test for shallow water leaks a.k.a. the dreaded rinse tank failure. This experience led us to standardize 3 different vacuum and pressure checks on every housing to weed out all failure modes.
Gates 'productized' the system in 2007 with the fitting name Seal Check. It was introduced in tandem with DEEP RED, our first cinema-grade system. We felt customers would appreciate peace of mind knowing their $50K+ camera investment was safe *before* entering the water. Seal check has proven itself many times, averting disaster from mistakes, abuse and damage (like from security inspections) that we all know happens in the field. For professionals it has not only saved equipment, but their production and paycheck as well. When you have to come back with the shots, failure is not an option.
As noted by others in this thread, the obvious benefits have resulted in the vacuum check system being adopted by nearly every manufacturer and several dealers (e.g. Backscatter).
Final note: The vacuum check system may extend all the way back to the 70's. I'm asking around to find out more....