These keys were turned to normal uncraftable keys after the event, and although some people will say that it appears as a limited summer keys on third party sites blablabla. But really:

Treated as normal key:

http://www.tf2outpost.com/trade/23200668

http://www.tf2outpost.com/trade/23254789

http://www.tf2outpost.com/trade/23251032

http://www.tf2outpost.com/trade/23215283

http://www.tf2outpost.com/trade/23201118

http://www.tf2outpost.com/trade/22524331

http://www.tf2outpost.com/trade/23249582

Selling for 9.33 which is what most normal key sellers are selling now:

http://www.tf2outpost.com/trade/23245738

http://www.tf2outpost.com/trade/23211066

Unsold at 9.66 ref:

http://www.tf2outpost.com/trade/23201033

Unsold 1 key 1 ref:

http://www.tf2outpost.com/trade/23256999

http://www.tf2outpost.com/trade/23215542

http://www.tf2outpost.com/trade/23250969

Plenty of unsold at 1.11 key in classified:

http://backpack.tf/classifieds/?item=Limited%20Late%20Summer%20Crate%20Key&quality=6&tradable=1&craftable=0

Since ppl will say "oh you need proof/sales" and whatever, here's one for you:

I sold 12 buds for 17 keys each, which 14 of them is the limited summer key (1 normal key each):

http://www.tf2outpost.com/trade/23010893