I bought this lens on ebay for less than 40 GBP and I have converted it to Sigma SA mount so I can use it on my SD10. I have to say that its an awesone lens...Sharp even when WO, very low CA, fantastic bokeh and increadibly well built with very solid all metal construction, but I would like to know a little more about its history, for instance: 1) Was it a very expensive lenses when it was first released? 2) Was it Canons best lens at the time? 3) When was it first released? 4) Is there any way to find out when my partular lens was produced? 5) Was there a particular camera was it meant for? Any help would be appreciated. Thanks in advance.