Its definitely not a shetland, they have never made any boat like that.
shelties dont look anything like this boat.
and shelties do not have the gull wing hulls, that the later 498 and family 4 and the black hawk hull types.
raider boats uses a hull shape the same as shetlands, and they are smooth and dont have spray rails.
the top if it was around 21 to 24 ft would bring coronet to mind, but not sure what it is.
it looks pretty nice boat, ive seen these before and not realy noticed a name on them.
im sure there was a blue one on ebay a few months back, but that was in bad condition.
the last time i saw one of these was a couple of years back down near brighton.