This is the information I have on changes made to the Indian Bicycle models. You can use this information to pin point the year of your bike (or close enough
1. Solid Hendee badge 1917 - 1923
2. Bracket-screw chain adjusters with flat dropouts 1916 - 1917
3. Split bottom bracket 1917 - 1918 (offered it as an option during 1919 and 1920 but the comun was one piece bb)
4. Straight rear fender bridges (1916 - 1917)
5. 4 plate (2 on top welded together) fork 1917 -1923
6. Diamond cups 1916 - 1922
7. Skirted fenders 1916 - 1923
Great find, it could be a tank or a tan-less model.