I just purchased this fly rod today and I'm stumped on who made it? It is a 9'4" Lake King and says Space Age Boron F6 9
I don't know the Lake King brand name, but 'Space Age Boron' refers to boron fiber, rather than graphite or fiberglass. Browning Silaflex made boron fiber rods with brown blanks, but so did other makers. In general, boron rods were fast
casters. I don't mean a predominantly tip-flex action, but fast as in the line whistles as it goes by your ear. Wear a good hat to protect your ears from wayward casts...
Given the markings, maybe try a 6 weight line. The Browning boron rods were marked with 2-3 line weights, so perhaps try a 7 or 8 weight line as well.