The Wiley Clapp Models 1751 and 1753 differ from the Model 1708:
1. A different main frame - the WC models are designed to accept the dovetail for the Novak rear whereas the 1708 is a standard frame that accepts the standard adjustable rear sight. (Same frame as the later Match Champion fixed sight model.)
2. The WC models have a contoured cylinder. 1708 has a straight cylinder.
3. The WC models have "melted edges" for easier holstering. 1708 has standard edges.
4. The WC models have a dovetail Novak front sight, either fiber optic green (1752) or brass bead (1753). 1708 has the standard removable front insert.
5. The WC models have a unique grip - special Altamont full size with unique laminate panels. The 1708 ships with the standard Hogue black rubber grip.
6. The WC models have a unique finish - 1752 has a Hawkeye Matte Stainless and the 1753 has a Hawkeye Matte Blue. The 1708 has a standard satin stainless finish.
The WC models and the 1708 all share the same common hammer, trigger, springs and action internals, although the WC hammers and triggers are finished in a matte stainless finish. The WC models are not tuned or improved over a stock action so you are not guaranteed any better in the premium WC models in that regard over stock.
I think that's pretty much it but if I missed something I'm sure someone else will be along to point it out. I agree $800 is waaaay to much to pay for a 1752 or 1753. They're still cranking 'em out so they're not rare or uncommon just really nice. I agree they are worth a premium but maybe $100 or so over a stock 1715. Interestingly the 1708s have been priced on the street a little lower than the 1715 from what I've seen. The 1708 may be a good buy unless you really, really want the Novak sights. All the other stuff can be modded after the fact.