Sorry for coming in late, it was a tough Summer for me. I have 2 M'15s marked to this same unit The two spikes are both stamped TB8. the center one has had the leather replaced on the chin strap.
I've always taken a stand alone F to mean that the helmet was regarded as for field use. Meaning it was quite up to quality standards. OYV helmets could be anything, the Volunteer could rent a helmet from the QM to purchase the top of the line. Check out the...