The endposts of this span are unusual and rather peculiar. It appears that pairs of angles are riveted to a flat plate to simulate channels. Pairs of these are then laced together with the edges pointing out. Seems like simple channels would have been better suited as they might not have degraded as badly as these "concocted" ones have.
Also Fish Belly floorbeams on a pony is rather uncommon, and suggests this span is likely pre-1900.
Would be a beauty if it were fixed up and placed on a trail somewhere!