That mdl. 650 with both (factory) .22 Lr and .22 mag. cylinders as noted by poster #6 above is very unusual and scarce...... Even more rare to find is the mdl 651 (adjustable sights) with both cylinders.
With two different production runs, of the 651, but with the conversion model only in the first, and an estimated total of 900 units total,( if I read the 3rd SCSW correctly).
Certainly not to be relied on completely, but Gun Broker had one listed with a start price of $1200.00, but do not recall if 650, or 651.
In my opinion, if you want it at $650.00 OTD, get it. You will not likely "walk up" on a better deal just around the corner.