I'm a bit late on this one but...
Pentax changed the position of the 'SFX' logo for the SFXn: The SFX has it on the outside of the battery grip (i.e. not on the camera body itself), the SFXn has it on the inside of the grip (i.e. on the rubber panel on the camera body itself). Thus, the SFX battery grips have SFX on the battery holder, the SFXn battery grip has no logo. Both are interchangeable. The model number I have for my 'SFX' battery grip (from the box) is '37001'. I presume the SF1/SF1n US model names are similarly different.
EDIT: The SFX (European model name) and SF1 (US model name) are the same camera, the accessories are interchangeable. Likewise the SFXn & SF1n are the same camera, their accessories are also interchangeable - and they all work with all four models.
Pentax also made the SF7 (cut-down version), I don't think there was an 'AA' battery grip available for this camera - it would be the only other Pentax camera that may have a similar battery holder.
Be careful when looking for an 'AA' battery grip, most of the ones advertised as such are actually for the Lithium 2CR5 battery - the AA grip is larger and has four chambers with contacts at both ends (the 2CR5 grip only has contacts at one end). It can be difficult to identify them from poor photos. The 2CR5 grip basically sits flush with the camera, the AA grip sticks out about half an inch.
John.
Last edited by johnha; 02-12-2018 at 06:26 PM.
Reason: Update for SFX/SF1 model names.