I acquired the EOS1n RS a few months ago, in a kit with a 24mm lens which I subsequently sold – the seller said it was a good camera for street photography. Hmm. The RS is a version of the EOS1n fitted with a fixed pellicle mirror like the Pellix and EOS RT (and the Sony SLT's). I always thought RT stood for Real Time. I'm not sure what RS stands for. It has the 8 AA battery Power Booster PB-E1 permanently attached, with blanking plates where the fixing wheel would be on an EOS 1n, giving it (to me) something of the air of a prototype. The whole idea being to achieve the fastest possible operation – the Canon Camera Museum has more about it: EOS-1N RS - Canon Camera Museum When the EOS 1v replaced the 1n, there was no RS version made as Canon apparently thought the 1v was fast enough as it was. EOS1n RS, 28-80mm Ring USM In use the most noticeable thing is that the image in the finder is darker than that of a normal SLR and it does not black out during exposure, although it does dim to the taking aperture. The RS was fitted with a 28-80 zoom – the early true USM version with metal mount and distance window. The subject matter, vintage vehicles at the latest Classic Vehicle Show and Autojumble, did not exactly stretch the capabilities of "the worlds fastest AF SLR" but there you go. Triumph Ford Classic Austin 7 Riley Triumph Mayflower I can't remember --- its American though Velocette - that's all, thanks for looking.