[New thread created to avoid derailing Moronic's review of his Mercury.]
I have several bikes from Continental makers and all of them have the frame lock fitted as standard on the front of the seat stays, so I assume they did that deliberately because they think that's the "right" place.
I can't see their reasons, unless it is a few grammes of weight distribution. With the lock on the rear of the seat stay, the customer needs to bend less far to operate the lock, a consideration for pregnant women and old folk, is less likely to get his hands dirty because the seat stay in conjunction with the coat guards* often fitted to Continental four-seasons commuter bikes keeps most of the dirt lifted by the wheel off the lock. I suppose it is done that way because on the rear of the seat stay, the lock will interfere with rim brakes. Not impressed: the brakes can instead be fitted to the downside because the customer needs to handle them less often than the frame lock. And, anyhow, that class of bike is usually built with disc or roller brakes, as mine are; it's only eccentrics like me who insist (because I found disc and roller brakes too sudden for an easily distracted cyclist) on Magura's rim hydraulics which are service-free for life except for changing the blocks at about 10,000km.
* A transparent plastic half circle filling in the mudguard shape over the wheel on each side from about parallel to the ground at the forward end to about 30 to 45 degrees behind the top of the mudguard; default standard fitting on Dutch city bikes(stadsfietse) and vacation bikes (vakansiefietse = touring bikes, look the same as a Dutch commuter but is much more luxuriously fitted out). Scroll down to the photo of my Gazelle Toulouse at
http://coolmainpress.com/BICYCLINGgazelletoulouse.html, and here you can scroll down to the photo of the rear of my overtly more sporting (to a Dutchman!) Benelux-only Trek Smover (electronic automatic gearbox and electronic adaptive suspension), with a coat guard, at
http://coolmainpress.com/BICYCLINGsmover.html. Both are vakansiefietse, too expensive to commute on if you have to park your bike at the station or outside the office.