The special offer intriguingly comes straight from the Microsoft Store. If you are in the US or Canada and purchase the MateBook from there starting today and until September 11, you will receive the Huawei MateBook Portfolio Keyboard for free. That's a $129 value, so a very good deal indeed, especially so soon after the device's launch.
Obviously as with all such offers, this one too is "while supplies last", so it may in fact end before September 11 if there are very many takers. As a reminder, the MateBook is priced at $699 with an Intel Core m3 processor, 4GB of RAM, and a 128GB SSD. Bumping the CPU up to a Core m5 and keeping the other two options intact means you'll have to shell out $849. Grabbing the MateBook with the same m5 but 8GB of RAM and a 256GB SSD will cost $999, while the most expensive option comes with the Core m5, 8GB of RAM, and a 512GB SSD for $1,199.