The serial number you list is 3000 higher than is shown in the Standard Catalog of S&W... is it possible you read it wrong? According to the list at the back of the book, the highest non-alpha SN should be about 786XXX which came at the end of 1969. The grips with "large diamond" around the screw were discontinued about 1968 and the alphanumeric SNs began about late 1969, so unless your serial number is off by hundreds of thousands, I'd place it in 1968... of course the book has some mistakes, so I would guess your number may actually be OK, but I'd still make it a 1968 gun.

As far as condition, the blue on yours looks pretty good for a shooter (if not so much for a collector) and I would just keep it clean and well oiled or waxed while enjoying shooting it. I have one a little earlier and gave a similar 30-1 to my littlest niece. She loves it as does her husband... these little guns are great shooters.

Regards,
Froggie