The (TAG) Heuer Monaco CAW211A 40th Anniversary special edition came with 2 straps that had those spring bars on them... and a spring bar tool in the box, too... Seems like a good idea if you're swapping the straps regularly and don't want to risk scratching the inside of the lugs with the spring bar tool...
Old thread I know but a subject I have been investigating. As @Archer says above these lever spring bars were OE fit by Omega in the 60's. Perhaps that's what the elongated channel is for in the no 6 end links. For authenticity these bars should be £500 each!!
Even with those slots, the handles turn so you can't get at them...I hate those spring bars with a passion. They should only be used on straps that are made for them IMO...
These quick-release style spring bars are fitted as standard to most straps made by Hirsch.
Echoing @gophishin ‘s point, you have to be careful if your watch has short lugs, as the shank can leave scratches on the underside of the watch case - as happened to my Longines La Grande Classique. I’ve also had a shank snap off at the base, resulting in me having to cut off the strap to remove the spring bar.