Now there’s a mystery!
I looked up the location on Google maps where I removed one of these around 1977- 99th St 2nd ave and much to my surprise the building is still there! but even more surprising is, none of the lion keystones is missing, nor are their patches in the wall where the holes were! As I zoomed in on the facades, nothing looks like anything had been replaced, yet in my 1977 photo I can clearly see 4 holes in the wall over the fire escapes, I only remember removing one because it was way up in Harlem and quite a bike ride up there, the window on the upper floor over the fire escape clearly shows my usual hole in the wall digging down from above and removing the bricks above and behind to pull the keystone up and in.

So I thought, well there’s new building a block further up on that side of the street, maybe somehow I got 99th street mixed up with 100th street, but the old Bromley fire insurance map for that block doesn’t jive for that scenario as it had 24 foot wide lots with 24 foot wide buildings having 4 windows across, the 1977 photo and the map shows 99th street having 40 foot wide buildings with 6 windows across, so it’s the right block, and in the 1977 view the corner building was gone- just a vacant lot and in the street view is a new high rise building there.
Now that’s plain wierd, and it means that somehow exact antique replacements were found (unlikely) and installed in the holes, or they hired Boston Valley to replicate them- possible but VERY costly, and these tenements were not historic or anything of the sort.

99th St 2nd Ave, ca 1977

99th St 2nd Ave, 2018

Detail of one of the lion keystones.

I don’t have an explanation for how the holes were filled up and the 4 lions I know that were removed are back in the wall as replicas or who knows!