That "approximately" is too approximate.

2.125 lb / 20 is 1.7 oz, which is very different than 2 oz when it comes to eggs -- egg sizes (in the US) are by the quarter-ounce, the difference between the two is two egg sizes.

(Which is how the problem in the article was solved -- eggs are now sold by weight, indirectly, because egg sizes are determined by weight, and you now buy boxes of eggs of a specific size.)

So the average egg in 1886 in that article would be classed as "small" today.