I was once told by the guys in Manchester airguns they were the main importers of FWB and a special batch was imported with walnut stocks (seem to recall 150 mentioned).
Sure someone else will be able to shed some more light on it or maybe ring up the guys at MAG as they are still there.
ATB Chris
Falcon Raptor (FN12) Lighthunter - Walnut FX Cutlas - EB XVI - HW35 'Karbine' - BSA Airsporter MK4 - Webley Mk III - Relum Tornado - FWB Sport 127 Deluxe - Crosman 1322 custom - Sussex Armoury Jackal - BSA Superstar - Logun Eagle (All .22) and HW80 in .25