The ornamental design for a tinsnip, as shown and described.
FIG. 1 is a perspective view of a tin snip showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top plain view thereof; and,
FIG. 7 is a bottom plain view thereof.
The dash-dot-dash broken lines illustrate the bounds of the claim and form no part thereof. The evenly-spaced broken lines illustrate portions of the tin snip that form no part of the claimed design.