27xxxx serial number means it was made in the late 70s. Full cinemod done by Duclos, so it has a hard EF mount, declicked aperture ring, permanent delrin focus gear, and 80mm front ring with 77mm threads. Everything is crystal clear other than the faintest cleaning marks on the front element and very very minor internal dust. Focus and iris rings are perfectly smooth.
Iris does drift very slowly towards a 4 when set at 2.8 though. Or you can just tape it. Paint on the barrel has some wear on it. The item "Duclos Cinemodded Leica ELMARIT-R 28mm f/2.8 #2726589 (EF Mount)" is in sale since Tuesday, December 4, 2018. This item is in the category "Cameras & Photo\Lenses & Filters\Lenses". The seller is "ct_skier12689" and is located in Austin, Texas. This item can be shipped to United States, Canada, United Kingdom, Denmark, Romania, Slovakia, Bulgaria, Czech republic, Finland, Hungary, Latvia, Lithuania, Malta, Estonia, Australia, Greece, Portugal, Cyprus, Slovenia, Japan, Sweden, South Korea, Indonesia, Taiwan, Thailand, Belgium, France, Hong Kong, Ireland, Netherlands, Poland, Spain, Italy, Germany, Austria, Bahamas, Israel, Mexico, New Zealand, Singapore, Switzerland, Norway, Saudi arabia, Ukraine, United arab emirates, Qatar, Kuwait, Bahrain, Croatia, Malaysia, Chile, Colombia, Costa rica, Panama, Trinidad and tobago, Guatemala, Honduras, Jamaica, Barbados, Bangladesh, Bermuda, Brunei darussalam, Bolivia, Egypt, French guiana, Guernsey, Gibraltar, Guadeloupe, Iceland, Jersey, Jordan, Cambodia, Cayman islands, Liechtenstein, Sri lanka, Luxembourg, Monaco, Macao, Martinique, Maldives, Nicaragua, Oman, Pakistan, Paraguay, Reunion.