HTC unveiled its 2015 flagship One M9 in March. During the release, the company showcased nearly 10 short promo clips of the device in collaboration with actor Robert Downey Jr., said Phone Arena. Following the promo, the tech giant has now unveiled a special edition HTC One M9 with Robert Downey Jr.'s signature engraved on its back.

HTC is reportedly giving away seven One M9 smartphones with Robert Downey Jr.'s signature via a contest. Notably, the contest ends on June 30. Interested readers can enter the contest by creating a “photo, video or other content [tweet] that displays what you love about the Robert Downey Jr. series and how the films have inspired you to create something new." After building the content, participants are advised to add the hashtag “#HTCxRDJContest” and upload the creation on social media like Twitter, Instagram, Google+ or Vine.

However, winners of the contest will not be chosen randomly. A panel of qualified judges handpicked by HTC will reportedly be determining seven lucky entries based on three criteria. This includes the “quality of submission” (33 percent importance), “originality / creativity” (33 percent) and "fit to contest theme" (34 percent). Moreover, the chosen winners will apparently be announced around July 13.

This HTC One M9 contest is specific to the U.S. residents with age criteria of 13 or older. Potential participants can check out the official rules list from these links: HTC One M9 Contest and HTC One M9 Official Rules.

Meanwhile, here is a quick recap of the HTC One M9 specifications. The device features a 5.0-inch display aided by 1080p screen resolution. The M9 is powered by a 64-bit, octa-core (Snapdragon 810) SoC and backed by a good 3 GB of RAM. Furthermore, there is a huge 20 MP rear-facing camera unit with dual-LED flash and a 4 MP Ultrapixel shooter at the front. Plus, the handset runs on Android 5.0 Lollipop OS, along with HTC’s latest Sense 7 UI.

Speaking of color choices, the HTC One M9 can be availed in gunmetal grey, silver/rose gold, pink/gold and amber gold. When it comes to battery specification, the handset comes equipped with 2,840 mAh battery unit. Lastly, the handset comes with 32 GB of built-in storage and microSD card support for further expansion of up to 128 GB.