Not Radioactive, but Roboactive

https://backpack.tf/item/1678143884

Sale 1) Sold for a Sunbeams Industrial Festivizer (51.5 Keys) + ~1 Key of Items

https://backpack.tf/profiles/76561198141455733#!/compare/1501545600/1501632000

51.5 + 1 = 52.5, which rounds to 53 Keys

Festivizer Mini

https://backpack.tf/suggestion/59e56829cf6c7575f9289e10 - 51.5 Keys

Sale 2) Sold for 49 Keys

https://backpack.tf/profiles/76561198095407289#!/compare/1501632000/1501718400

Sold fairly quickly and is countered by the Buyer below.

Sale 3) Sold for 51 Keys + 15 Refined

https://backpack.tf/profiles/76561198041902665#!/compare/1505174400/1505260800

Countered by the Buyer below.

Sale 4) Sold for 45 Keys

https://backpack.tf/profiles/76561198002757046#!/compare/1506297600/1506384000

Countered by the Buyer below.

http://www.tf2outpost.com/trade/29269924 - Buyer at 51 Keys + 21 Refined

http://www.tf2outpost.com/trade/29307349 - Buyer for either 43 Keys or 51 Keys

I'm using the Buyer at 51 Keys + 21 Refined to counter the sales below it (the second Buyer could also be 51 Keys), but they support such a steep drop.