This is a crew boarding ladder/platform for a B-58 hustler. The platform section of the ladder was at the level of the open crew position hatches.
Attached is a photo of the Hustlers at I think Carswell AFB, TX (note the flatness of the area). Also attached are more close ups of the platforms and the A/C.
Statistics for the Hustler are:
Length: 96 ft 10 in (29.5 m)
Wingspan: 56 ft 9 in (17.3 m)
Height: 29 ft 11 in (8.9 m)
Hope these help.
Steve Payne, USAF Ret
P.S - Will have to send boarding ladder photos as separate messages.