I found mention in a couple of obscure places that the reference to the Baltimore precancel invert holds true for the other experimental cities as well, so basically the values are the same regardless of what inverted experimental precancel is shown.
Interestingly, I went back to a very old Scott Specialized Catalog I have (2002) and there is no listing at all for the inverted precancel; my Scott Specialized (2011) shows the listing but without any value either mint or used; my Scott Specialized (2013) shows the mint value at $700 in
italics suggesting that the item is difficult to value accurately (or trades very seldom), which essentially brings us back to supply and demand theory: The true value being what a buyer is willing to pay and a seller is willing to accept for the item.
Here's an eBay reference for you with the Memphis invert precancel from a dealer. It shows a BIN price of $349, which is basically 50% of Scott catalog for the inverted Baltimore precancel listing. (This further supports the idea that values are basically the same no matter what inverted precancel may be shown on the stamp.) Of course, the eBay listing shows no bids, so it may be that even though the variety is "rare" if there is not popular interest in acquiring the item, the value may be questionable if there is not significant enough demand for the item on the secondary market.
http://www.ebay.com/itm/1384-Variet...em2ec633e775