Most likely the colors/prints of canvas vary by each "batch." However, I'm wondering if the thickness issue really just depends on what the canvas is bonded to on the backside/interior side. I believe they changed the canvas around 2008 to be more flexible (likely thinner) to accommodate the newer styles with pleats and folds. However, I think they use this same canvas for all their items (can you imagine the cost of having multiple thicknesses/gauges of canvas). It's just that some of the items are backed with nothing or fabric or alcantara or leather, so the outer vinyl-coated canvas just seems thinner/thicker on some items, though probably just depends on what it is lined/backed with (bad grammar, sorry).