Activates on Steam; use the voucher code to reach prices in title. There was also an offer of $1 cashback or $2 GMG credit upon purchase that doesn't seem to show anymore.
Link for normal version is http://www.greenmangaming.com/s/au/en/pc/games/action/hitman…
From the GMG website, the Professional Edition includes:
a 72-page Digital Artbook
A Behind The Scenes "Making of video"
"Agency Gun Pack" DLC, which includes an upgraded silencer and laser sights and the following exclusive weapons:
Agency Jagd P22G: A modern top-tier pistol
Agency HX UMP: Powerful high-caliber SMG
Agency SPS 12: Brutal semi-automatic shotgun
Lasts 24 hours, prices are in USD.
Blind buy for me this and the price is reasonable :D Thx OP!