The street price on the lock version of the current PC 657-5 is $850 and up.
The information I have says that 150 of the pre-lock Performance Center 657-4 Defensive Revolvers were produced for Lew Horton Distributors in 1999. So I would think the small production number would be worth a little extra over the current model...if you can get it for less than $850 it's a good deal, $850-$1000 is still ok.
Roboto, to answer your email about the Ahrends grips on PC 657-4 (upper left in photo below).
They are very concealable and comfort and control are good with 220 cast bullets at 1000fps. For better control I do prefer the finger groove Ahrends (upper right) on the Jovino 657.

L.L., Altamont grips on Jovino 57; L.R., Hogue grips on LH 657-4 3" Full Lug
KO