I can tell just by placing it on my wrist with no strap, that it seems like it's going to wear better than even the 6309 diver or the well fitting Tuna, so I'm very happy with finding this NOS sample case (Pic Below).
To be honest with you,
I do love the quartz Tuna's very much so, and mine fit & feel and wear great on my wrist. Which never having one ahead of time to test, was sort of a big gamble with the unknown but it worked out well for me.
They are perfect on my wrist especially the Big badboy SBDX005 600m auto 8L35 King Tuna.
~ The thing is as you know, they are real Dive Tools meant for commercial diving and best suited in that wet & dry suite environment.
Although I do realize, that the Tuna Diver just doesn't fit or suite everyones wrist the way they would like them to, as you have mentioned about the fit and feel of your Tuna's.
lol, To wear them with a shirt & tie is kinda off the deep-end as we know, but hey it sure is worth trying at times isn't it!
Back on Topic,
I feel these 7C46-6009's are extreamly rare watches, and from what I see of the sales and prices realized of their Tuna cousins, I think that a NOS fully functional example should be worth $1200.00 usd or about $600 pounds sterling my friend!
I could use any (help or heads-up) email, if you hear or see something that I really need or would be looking for like a 7C46 movement or a beater SSBN007 to barrow the machine from her.
~ I really appreciate that kind gesture from you very much so & it's always worth while to find caring friends on this or any other forum!