This time round, I have some cellphone pictures of a Seiko SQ Sports 150 model to share. From its serial number, I believe this model was released in 1988.
Side profile.
Caseback shot. Excuse the wrist cheese.
It comes with a screw in crown.
Bracelet and clasp.
The shape of the end link reminds me of the 6309-7040. I don’t think this will fit the 6109 though.
Yeoman's Weblog 
I have this exact model, purchased in Hong Kong at the beginning of 1990, and it has a serial number that suggests it was produced in 1988, one month after yours. My version has a flat rubber dive strap. It’s on my desk right now, waiting for a battery change. Thank you for posting photos, it’s good to know examples of this model still exist.
I have a 1987 Seiko my father gave me a few years back. Little rougher than that one, but Its really valuable to me due to the history and the age.
Thanks for posting. Take good care of the watch.