Does seem to be a merc thing though - was it a 208 or 124 coupe with R129 front end someone posted a month or two ago. Also SEC bonnets on 190s/124s and 124/SEL bonnets on SECs etc crop up regularly.
IIRC this one was the LHD model, european version, and Japan as well, the 202/203 one. They've done only couple (hundreds) of them, whilst introducing the new 203.