I think it's Yamaha. Not a Daytona. Thought maybe XS650 but only 4 bolt holes. Looks to be of the same age/period as the RD rotors. Thick like the RD rotors. LC? Banshee? ATV? Google wasn't much help.
(https://lh3.googleusercontent.com/pw/AM-JKLXdkghCZyZv_pzmUsk5tJ2UGXKbzlMUSVwVg9koIsa26YegUi53hyag28h4cc5o5llNtrKT9zqYm6_jvUmnPHQzMLAEoYmjl9IEPBurawBwsr7dWabXI6pzdV8l1uWVsTF_fm2KfdUgqCZ88QmH78HS=w877-h899-no?authuser=0)
If my google-fu is strong, I believe it is a rear rotor from a 1978 Kawasaki kz1000 Ltd.
or even a 76 kz750 twin :) but actually it's a kz rear brake rotor 76 thru 79 I think. Kz 650,750,900 and 1000
(https://i.ebayimg.com/images/g/mJ8AAOSwcHdhQjqb/s-l1600.jpg)
That sure looks like it, thanks
john
yeah i was going to say kawasaki. they also fit some of the triples.