It’s not a medieval weapon. The 1930’s Tree Climbing Spikes, or gaffs, with straps are marked “16 M Klein & Sons.” These were also used while servicing telephone poles. Here is a photo of telephone electricians learning to climb poles in 1914.
(Source Image URL from retronaut.com)
Watch this internet pole trainee learn proper climbing technique by the line crew.
(Source Video Embed Code from http://youtu.be/vxcoEivCTZc)