Hough ha payloader

hello, I’ve recently started fixing up this payloader ha. I believe it to be a third gen. Under the seat appears to be a reservoir of some type and the fill tube for the transmission. Can anyone tell me what type of gear oil/transmission fluid belongs in there and what the reservoir is. It appears to be a filter, I’ve never seen one like it, any help would be much appreciated, I’ve posted a pic

John

Hough ha payloader