The Finnish mobile startup Jolla has taken the wraps off its initial smartphone, the long-awaited device which will be the first to run the Sailfish OS .

Jolla announced on Monday that the device is available for preorder, and will come with a back plate that will allow the phone's UI to be customised.

It has also released some of the smartphone's specs. The phone will run on a dual-core processor with 16GB of onboard storage and an extra SD card slot, and will include an 8 megapixel camera and 4.5-inch Estrade display. Jolla, founded by ex-Nokians, says the mobile is 4G compatible, but that will depend on carrier support.

Jolla is not giving away too many technical details at the moment, as the company hopes the device will compete on user experience rather than hardware features, according to Jolla's recently-appointed CEO Tomi Pienimäki .

"We would really like to avoid the hardware details... If you look at all the vendors producing Android phones, to me it seems hardware is the only way to compete because that's the operating system that everyone has," Pienimäki told ZDNet. Minor technical details could change before the device shipped, he said.

The pre-order device is only available to buyers in Finland, Sweden, Denmark, United Kingdom, Germany, Spain, France, and Italy priced at €399 (£337). It's expected to ship by the fourth quarter of this year.

Those wanting to be the first to get their hands on it can pre-order with a €100 downpayment, which will gain them a €100 voucher off the overall price and "priority pre-order status" on the device. Pre-orders will also get a chip-embedded cover for the phone called "the OtherHalf". A €40 pre-order package is also available, which gets the buyer a Jolla T-shirt and priority pre-order status, but no OtherHalf cover.

Although the OtherHalf acts as a back cover, it could become a key plank in Jolla's pitch to retailers, brands and operators seeking to customise the user experience, according to Pienimäki.

"When you put these two halves together, it also changes the look and feel on the software side," he said. "There's a chip on the OtherHalf and when you put that on the phone it affects the software side of the device. That's why we avoid calling it a cover."

Pienimäki said that a music group, for example,k could launch an album and offer a customised user experience with the OtherHalf. The cover would not actually store the music but act as a key to unlock content hosted online.

The cover would become part of Jolla's soon to be launched "co-creation" campaign with the user community.

"We'll ask them how do they want us to develop the OtherHalf," he said. "We do not want to decide it ourselves. We want input from out users and community... for instance, about the colours of the cover."

Jolla plans to expand the €100-and-OtherHalf offer to other parts of Europe later, and hopes to use the pre-order campaign to gauge countries' interest in the device, to help decide where it might launch next.

With the devices soon to be in consumers hands, Jolla is now working out how customers can install Android apps on the devices.

"There are two questions. One is that Android applications can run on Sailfish and then the other question is 'Where do I get it?'," Pienimäki said. "That's an ongoing discussion at the moment. Because now we can run the Android application, and then it's a question of agreeing with whoever the partners are that the user can download the application from 'app store X'. There are quite a lot of stores where we can get Android."