How to date Filarmonica straights

[BWR]

Hey guys I'm curious on how to date these straights as I heard the early ones was the best. Any help is much appreciated!

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[pvsampson]

Fili love what makes it so good!

 

[BWR]

Thanks so much for this info it answers my questions. You guys are great thanks again

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[stone and strop]

60's -70's