Having looked through the discussions on this page I perhaps can contribute a little bit. Finnish history as far as genealogy is concerned is very well documented, church records are kept from at least 17h century and there is a project going on where volonteers are putting them all into internet searchable format. You can try this Finnish genealogy site: http://www.genealogia.fi/indexe.htmhttp://www.genealogia.fi/indexe.htm , it is the english version, and explicitly http://www.genealogia.fi/hiski?enhttp://www.genealogia.fi/hiski?en ,there select the geographic area of Finland, if known, or 'ALL' and then enter last name or whatever is known. Wildcards also usable. Seems than many Koski's shortened their last name after emigrating - 'Koski' means 'rapid' and may have had a pre or a post part in the Finnish original name like 'Koskimies' , Kellokoski'. Good hunting !