Hammerdown,
I agree: I think a 6" blade is optimal and I also love the fingergrooves. Here are a couple of e-bay reference points:
This first (1-6) knife is a few years later (maybe mid 70's). No fingergrooves, but it's near mint.
http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA%3AIT&rd=1
This next one is the closest: A 1-7 with 7 spacers and fingergrooves same era as Brome's again near mint.
http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA%3AIT&rd=1
Here's an older 1-8 with Heiser sheath in pretty poor condition.
http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA%3AIT&rd=1
Condition is always a big factor unless as I mentioned there was Vietnam Provenance to go along with it.
Best,
Ron