In a Steam blog post, Valve announced a milestone for its upcoming handheld, the Steam Deck: dev-kits are already being shipped to said developers.
Manufacturers tend to do this ahead of official release, giving developers time to go hands-on with the hardware and its software stack, try their software on the device, and learn about quirks and performance bottlenecks. It also opens up a more direct line of communication, and lets developers give Valve direct input on the Steam Deck as it enters the final phases of development.
Valve also published a handful of pictures of the Steam Deck dev kits on their way to packaging:
This announcement happens a mere two-and-a-half months of hands-on time developers will have with the Steam Deck ahead of its announced general availability on December. Games console dev-kits are usually delivered much earlier than that. However, the Steam Deck is an outlier not only in its form-factor; it's an outlier in that its hardware is already very well known by developers. The AMD Zen 2 CPU, AMD RDNA 2 GPU, and memory and storage subsystems have been studied to death on the latest-generation PS5 and Xbox Series X consoles already, not even counting on the PC development space. Developers won't be trying to grasp an entirely new architecture and entirely new functions as they would for a typical console launch.