I've done a bit more research on the Sharpfinger sheath styles. Schrade production records are mute on the subject of sheath changes and factory catalogs are suspect due to lithographers reusing old artwork. At best, we can pin the changes down to "circa" using dated examples which are mostly SFOs and limited editions. No doubt there was often overlap in the style/type used as sources and in-house inventories changed.
There were three basic sheath types. The first had a minor change early on, the shape of the end of the choil retainer strap. I find no record of part number or dealer/customer order I.D. like I do on the last two sheaths identified as accessory sheaths sold as replacements, SAS-17 and SAS-19. So I have given each style an arbatrary identifier, T-1, T-2, T-3 and T-4.
T-1: This first sheath style is noted in early (1973) catalogs and on flyer artwork as well as examples up to 1976. Many of the production sheaths of this type used contrasting white stitching.
T-2: This revision of the sheath, rounding the tab of the choil retainer strap, is first seen in a 1977 dated example though it did appear earlier in the 1975 flyer for the 152GD. It is last seen in a 1984 dated example though it continued to appear in catalogs and flyers for a few more years. Most of this type used color coded stitching as did the suceeding types.
T-3: This (SAS-17) pouch style sheath first appeared in 1983 dated catalogs, flyers and examples. The last appearance I have found so far is an 1987-88 example (502SC) and 1986 flyer. As seen on a few dated examples, some T-4 sheaths were used concurrent with the T-3.
T-4: This last sheath type (SAS-19) with handle retaining strap was first seen in a 1984 catalog, 1985 flyer and 1985 dated example. It was used with very minor construction changes through end of production in 2004.
Several special sheath textures were tried (mostly in the T-1, T-2), though none were adopted for regular production. Likewise colors of leather.
This trivia is only important in that it gives us an additional means (when the sheath is original to the knife) to approximate the date of production of an example. Since the same woodgrain fold down box was used for so many years (1973-mid 1980's) they have limited utility in dating. Likewise the tan box (c. mid 1980's - 2000) was used over quite a period of time. The blue stripe box saw only and approximate two year use (c. 2001-2002) as did the last blue/grey box (2002-2004). As always, an original enclosed brochure is the best indicator on a NIB non-SFO, non-limited edition Sharpfinger.