I've been tidying cupboards in the Club armoury and have found a tin box of bits which I've tentatively identified as BSA Martini spares - a variety of items which could easily pass as medieval torture implements. Coil springs, pins, trigger blades, various complicated but extremely sturdy lumps of metal which are almost certainly the extractors you describe - although the chances of them being Mk 1 are probably slight. If there are any images or measurements, let me know and i'll have a hunt. Probably going to unload them as a job lot on ebay unless someone can suggest something better - no use to us any more.
Patrick