5513...early 60's?

[Cloudchaser]

I have the opportunity to buy an old Rolex but know nearly nothing about vintage Subs. Getting pictures at all has been tough (dude is old and technically challenged and difficult to contact), so the attached picture is all I have at the moment.

The price is an amount that I'm not real worried about (if it turns out to be something awful I'm not going to cry) and the source is more than reliable (this old dude is legit!), however I've never ventured into these deep Sub waters before.

Can anyone tell me anything meaningful from this lone picture? I'm inclined to just buy it and figure out details later...which is likely what I'll end up doing here, but could someone perhaps narrow a year (or range)? It is a 5513 with a serial number of 1.6M. As a more modern watch guy, it just looks a mess to me...but I also understand that that has an appeal to some.

Thanks in advance!