Counter. The other suggestion would benefit me more, but I prefer to have an accurate price. :P

Never suggested for an Unusual before, though. Advice would be appreciated.

Sale 1: 27 keys pure

http://backpack.tf/profiles/76561198072246235?time=1451980800&compare=1452067200

Individual pages for those of you without the script:

Before: http://backpack.tf/profiles/76561198072246235?time=1451980800

After: http://backpack.tf/profiles/76561198072246235?time=1452067200

Credit to MrBliss for providing the following proof in his suggestion:

Sale 2: 30 keys (Sold for Overclocked Powdered Practitioner)

Trade screenshot: https://gyazo.com/5da51c0d748fb4b83c05057731eb9d41

Backpack comparison: http://backpack.tf/profiles/76561198083901668?time=1452153600&compare=1452067200

Individual pages for those of you without the script:

Before: http://backpack.tf/profiles/76561198083901668?time=1452067200

After: http://backpack.tf/profiles/76561198083901668?time=1452153600

Not sure with the 30 key sale since the Practitioner has a 4 month old price, but it's 1 of 1 and this is the only time it's changed hands since then. It's on the market by the owner, though: http://www.tf2outpost.com/trade/27672295

No other valid sales since the update as far as I can tell. Currently only one seller left on the market asking for more than he'll probably get.

Conclusion: 27 - 30 keys