Looks to be Scott No. RS167. I can't confirm the exact variety based on your scan, but my 2013 Specialized Catalog states value at $22.50 (R167b, silk paper) or $16 (RS167d, Watermark 191R). Of course, value is diminished considerably given the damage shown on your stamp.
A good indicator of value is what this example might have sold for on eBay
. As per the link below, an R167b recently sold for $4.25 on eBay
, suggesting that it realized about 19% of its catalog value -- and although it is stated to have had some thins, it has what appears to be considerably less damage than shown in your example:http://www.ebay.com/itm/Private-Die...047675.l2557
Certainly a "keeper" but not of tremendous value in the secondary market.
More information may be found here:http://www.rdhinstl.com/mm/rs167.htm