Great resource RIP. Langs will surely know somebody that can appraise the fly collection.
Just find somebody that is knowledgeable in artistic fly's.
I read or heard somewhere that these artistic tiers will purchase feathers from museums on extinct birds so they can match the traditions of the past. Your granddads streamers could be on the same level of those artistic flies. Some of these flys take hours to tie.
PS... I am still looking for the guides name in Toas NM. But my filing system is one step away for chaotic.