Notes:

1. Concavity.
2. Flat lower edge.
3. Curved top edge.
4. Region of higher elevation. This region appears to be separate from the symbol, possibly the result of deposition. The bottom section of this region extends below the expected bottom edge for the symbol based upon the adjacent symbol.

A 1 needs a narrow width, horizontal top. There is no support for this as symbol #17 has a wide curved top. A 1 needs long vertical edges. There is no support for this in symbol #17. This excludes a 1.

A 3 requires a short edge to the top left, a concavity on the right-hand edge, and lower curvature, none of which appear to be present in symbol #17. This excludes a 3.

A 4 needs a left-hand vertical edge, or a diagonal from the middle-left to the upper right, and a vertical right-edge. There is no support for any of these features. This excludes a 4.

A 5 needs a wide horizontal top, a top-left corner, and a short left-hand vertical edge from the top. This is no support for any of these features. This excludes a 5.

A 7 needs a wide horizontal top, and a diagonal from the lower left to the upper right. There is support for neither. This excludes a 7.

A 0 requires a curved top which symbol #17 has, and also requires a curved bottom, which symbol #17 does not have. A 0 also requires either convex or straight left and right edges, neither of which are present in symbol #17. This excludes a 0.

A 9 requires a closed loop on the top. While symbol #17 has top curvature, which is a portion of what is required for a closed top loop, this level of detail is not visible in symbol #17. A 9 also requires a diagonal line from the lower-left to the upper right, and a narrow, horizontal foot. There is no support for this in symbol #17. This excludes a 9.

A 6 requires a left-hand straight vertical edge, or convex edge. Symbol #17 has a conflicting concavity on the left edge. A 6 requires a lower loop which lower curvature, whereas symbol #17 has a lower straight edge. There is no support for these features in symbol #17. This excludes a 6.

An 8 requires a closed loop on both the top and the bottom. Symbol #17 does not appear to have a closed loop on the bottom. This excludes an 8.

A 2 requires a short edge to the top left which may be present in symbol #17. A 2 also requires top curvature which is present in symbol #17. A 2 also requires a diagonal from the lower-left to the upper right, however this level of detail is not visible in symbol #17. A 2 also requires a wide flat bottom, which appears to be present. A 2 is a possible candidate for symbol #17.

Outline: The yellow overlay is the visible portion of the symbol’s outline. This overlay is the partial outline for a “2” which is supported by the evidence.

Conclusion: The symbol features suggest TIGHAR artifact 2-6-S-45 symbol #17 is probably a two(“2”). The most likely first alternate is a nine “9.”