Serial numbers only give a rough indication of when the drums were made. There is a chart elsewhere on this very site that can help you find that year. Click on the Slingerland Drums link at the top of this page for lots of useful Slingerland info including (if I recall correctly) a serial number timeline.
Those drums would be similar to the ones that Buddy played from roughly 1968 to 1978 but that doesn't appear to be a "Buddy Rich" set which had two floor toms, double spurs, an extra cymbal mount, and other details similar to Buddy's own kit. The actual BR sets do often bring a premium over more typical Slingerland drums. That might be the Gene Krupa style set-up which was a standard sized 4 piece set.
Vintage Slingerland drums in general tend to be less expensive to buy than other brands of the same vintage such as Ludwig, Gretsch, or Rogers. As such they can represent a great value to someone wanting to own a set of vintage drums, although it's not so great for someone with a set to sell. Quality wise they are typically every bit as good as the other American brands. The lower demand (and hence value) probably relates to the fact that the brand has had such a low profile since the mid 1980's when the original company went under. Gibson currently owns the name and has made and marketed Slingerland drums on occasion during the past 25 years, some of very high quality, but they were never widely distributed.
That does look like it could be quite a nice set if it is as described (one owner set that was probably well cared for). I only tend to buy cheap and never sell anything so I'll leave it to others with their fingers tighter on the pulse of the market to opine on value.
