UPDATE: Number of magnets
Reposted due to images not being visible.
I had a few requests to count these magnets. Weighing a few, then all of them, seemed like a good suggestion. Unfortunately our scales just aren't big enough. So what I've done instead is measure their height. It's not quite as accurate, but should give a fairly good indication.
Apologies, I've used metric. If you want to follow along with a unit that's more familiar to you, the conversion you'll need is: 1mm = 0.0000110936 football fields.
A 50mm stack contained 77 magnets. Each magnet is therefore 0.65mm thick.
I've got ten complete small stacks that average 115mm tall.
There is an incomplete small stack that, currently, is 81mm tall.
There are 4 large stacks that are exactly 400mm tall.
115mm x 10 = 1150mm
81mm x 1 = 81mm
400mm x 4 = 1600mm
Total height is 2831mm (or 0.031 football fields)
Dividing 2831mm (total height) by 0.65 (thickness of magnet) gives a grand total of 4355 magnets.