Phil Cater cross-kits the Matchbox HS125 Srs 600, and the Airfix Dominie, to create a HS125 Srs 400 in SAAF colours. Some other Srs 400 possibilities. Full descriptions and useful photos, (along with fairly dubious general arrangement drawings) can be found in Bill Gunstons' excellent 'Hawker - The story of the 125'. A Srs 400 model could also be finished in other military colours, such as the RAF 125 CC Mk 1, or an 'attack decoy' Argentinean HS 125/400B of Escuadron Fenix, not to mention countless civil schemes.

Radical surgery:

The Mercurius is a HS125 Srs 400. As such, it shares features with both the (Srs 200) Dominie and the 125 Srs 600. While it is possible to convert either an Airfix Dominie or Matchbox 125/600 into a Srs 400 by adding or subtracting various bits, I felt the easiest approach was to cross-kit them.This may not always be possible, as both kits are now relatively hard to find, and thus fairly expensive, so the various differences are fully described here to enable conversion of a single kit. In which case, the Dominie might be the better starting point for a Srs 400.