5 Belt loops, this is how many belt-loops a typical pair of jeans has. Two belt-loops positioned in the front before the front pockets.
501 LOT number Levi’s jean. 1853 Levi Strauss arrives in San Francisco and opens a wholesale dry goods business, selling clothing, blankets, handkerchiefs etc.
Arcurate Denim Encyclopedia
Big E, to collectors, Levi’s 501’s made before 1971, which have a capital E in the word Levi’s on the red pocket tab.
Five Pocket Jean. The total numbers of pocket a classic jean have; the classic jeans have two back pockets plus two front pockets and a watch pocket inside the front right pocket.
Watch pocket is the small denim pocket made its appearance in 1902 and has gotten progressively smaller since then due to the demise initially designed for watches.