I presume Peter will be referring to 'The Spirit of the Pike' by Graham Priest. It's a great book for anyone who is a collector of No.4 Spikes (and various others are covered). It's out of print and can be hard to get hold of nowadays.

The Singer release catch will probably of come about because of a refurb, originally it'll of had a Savage release catch on it. I think Singer did supply release catches to some of the UKicon based makers of MKII* spikes though.