I just bought a Linhof Kardan Standard with 2 lenses (135 mm f/3.5 and a 90 mm f/8) for $1400. The camera needs a rear standard with a ground glass and a rail between the two standards. I'm looking on eBay but I didn't find them. Can I find them new somewhere? Another question. Can we learn something with the serial number on the camera and on the lenses? Year of fabrication, etc. Thank you for any answer.