Interview with Elliott Hancock
Interview with Lynn McSpadden
Pinetop mentioned the McSpadden Interview linked above in another thread that mentioned dulcimers by McKinley Craft and that McSpadden's pattern came from a McKinley Craft dulcimer. The Hancock interview is part of the same web site which is an oral history of the Arkansas Folk Festival and the Ozark Folk Center.
In general, McSpadden dulcimers are not particularly sought after or unique (compared to a Ledford, Presnell, etc.), largely because McSpadden has made so many. Howver, they do have a good market on eBay and typically bring at least $200-250 on eBay and some go for a fair bit more (a 1989 recently went for $330).
You say the dulcimer you are selling was made in 1973. That would be the year the Ozark Folk Center opened and the year after McSpadden opened The Dulcimer Shop in Mountain View at the corner where the road goes up to the Folk Center. McSpadden had been making dulcimers for a number of years prior to that.
Hancock was a part of that move to Mountain View, perhaps as a partner, but I'm not real clear on that even after reading the interviews. He had been Lynn McSpadden's college roommate.
The dulcimer you are selling looks like it is pretty much the current design. Some pre-Mountain View ones have wooden tuners, a little different scroll head and some other minor differences. The tuners are a friction type tuner that was used until the very late 90s or possibly as late as 2000 on McSpadden Scroll heads. Current McSpaddens (since Summer 2006, I think) are all solid wood, but most older standard models used a high quality laminate (plywood) for the back and sides for consistency in tone. Not sure when McSpadden started using the laminate, but the photos (esp. the one of the head) and description ("all walnut with solid walnut face") in your auction make me think it must have been prior to 1973.