Hi Dirk, and welcome!!
Thank you for posting this spontoon. With these it is always helpful to have other images showing as much of the weapon as possible, and the foot piece as well. Although the staffs of these weapons are often replacements, it is always hopeful that the head and foot are still together.
This appears to be an American spontoon c.1775 (Neumann, "Swords and Blades of the American Revolution" , 1973, p.211, #73.PA). Are there crossbar curls on the lower part of the head?
The spontoon was the weapon of officers used as a means of identification and in signalling the troops.
"...when the spontoon is planted, the regiment halts; when pointed forward, the regiment marches; and when pointed backwards, the regiment retreats".
Quoted in Neumann (p.191) from "Smiths Military Dictionary" (1779).
Very nice
hope this helps,
Best regards,
Jim