Binder (2-prong with compressor bar, for 500-sheet capacity)

These are the binders you like. If someone would give them an easy name to remember, they could rule the world. I would call them "Annual Report Covers, Professional Quality" or "Thesis Binders" or "Book Binders" or "Professional Prong Binders."

They are:

Oxford 57301-05
Two-Hole Prong Report Covers
3 capacity (500 pages)

These come 25 per box (cost in 2018, $38)

This link calls them Esselte (may be a brand):

Oxford-57301-05 Report Cover at Amazon

https://www.amazon.com/Oxford-57301-05-Report-Covers-Capacity/dp/B00094GSJO/ref=sr_1_1?ie=UTF8&qid=1520383729&sr=8-1&keywords=Esselte+5730105+Report+Cover&dpID=41hBoCDsQ1L&preST=_SY300_QL70_&dpSrc=srch
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I don't think I like the pressboard as much. Stronger, but not as professional looking; kind of clunky and they tend to warp, I think. But here they are:

ACCO Pressboard Report Cover, Reinforced Hinge

https://www.amazon.com/gp/product/B005COZ2PC/ref=ox_sc_act_title_1?smid=A2J4ZFD90AWRCT&psc=1

https://www.amazon.com/gp/product/B00006IES5/ref=ox_sc_act_title_5?smid=ATVPDKIKX0DER&psc=1

Amazon also has them individually as add-on items, at about $1.75 per binder.

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Here's one at eBay. If the item is gone, I think the seller restocks it...

Prong Binder at eBay

https://www.ebay.com/p/Esselte-5730105-Report-Cover/144251930?iid=112802270945&_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D2%26asc%3D44039%26meid%3D0602cef593e14822829ad8a7a9d65f19%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D322360150396%26itm%3D112802270945&_trksid=p2047675.c100005.m1851