On the Internet, I have found a black and white postcard picturing jumpers climbing a wooden scaffold jump. The inscription identifies it as the Munising Ski Slide c-1928.
I have found a newspaper reference to installing a new, artificial surface on a ski jump in Munising in the Ironwood Daily Globe for June 23, 1960, and also a mention of the artificial surface (kind of like broom bristles) on a site called the Ski Jumping History Project. I have seen multiple references on the web to a postcard offered by Card Cow, a postcard sales site, that show a jumping hill with cars and spectators below. It says it is a picture of a competition at the New Ski Jump in Munising, and one reference dates it to 1969. The cars I can identify in the picture date from 1957 to 1967 or 1968.