Built between 2003 and 2009, the Mercedes SLR McLaren was a modern-day tribute to the 1950s 300 SLR. The super Gran tourer preceded AMGs SLS and GT models, both inspired by the 300 SL. Throughout its production cycle, there were some limited edition versions, such as the 722 Edition. There was also a race-prepped version of that, which you could buy. There is, however, a much rarer version of the Mercedes SLR McLaren, which was presented in a Seen through Glass video. It was developed by MSO (McLaren Special Operations) and now, one of the 25 made is for sale.