Jim,
The firearm in your photographs does not have a stainless slide.

It has been hard chrome plated after it left the factory.

There are several little telltale signs that it is not a original stainless slide

The most obvious are the extractor, slide stop and the hammer block

On your firearm they appear to be made from the same metal as the slide.

Even if the factory produced a single stainless slide, they never would have tooled up to produce a single stainless extractor, stainless slide stop and stainless hammer block. They simply would have used the existing blue steel parts that were already in inventory.

It is hard to tell from your photographs, but it looks like the barrel bushing has also been plated in the same finish

Whoever plated the slide also plated the small parts in the same finish, this is a common mistake with aftermarket refinishing companies.

The Model 745 and all of it's 9 product codes are well documented in the Standard Catalog of Smith and Wesson which is currently in it's fourth edition

Call the Factory. Give them your serial number, they will tell you the product code