Which is the most-awaited smartphone for the year 2013? There is just one answer - undoubtedly the Samsung Galaxy S4. And for that very reason, rumors surrounding specifications and release date of the device refuse to die down. However, Sam Mobile has confirmed that Samsung is busy testing the next flagship device with model numbers GT-I9500 and GT-I9505.

Revealing the first model numbers of the new high-end device, unofficially dubbed the Galaxy S4, the report said the smartphone will run on either Android or TIZEN, an open source, standards-based software platform.  "We know that Samsung's first TIZEN developer device is using GT-I9500 as its model number which could mean TIZEN is close to come, or, other possibility is that Samsung changed the model number of the next-generation Galaxy S device," the report said.

As Koreans consider number 4 to be bad luck, Samsung is believed to have decided to go with new model number and GT-I9500 is assumed to be the Galaxy S4 smartphone. GT-I9505 is presumed to be a LTE version. Given the fact that Galaxy S3's model number is I9300, Samsung would skip I9400 in favor of I9500. It should be noted that the South-Korean tech giant has never used the number 4 to name any of its high-end products.

Citing unnamed sources, the report further said that the company is currently testing software for both the aforementioned handset versions.

Model: GT-I9500

I9500XXALL1/I9500OXAALL1/I9500XXALK3

Model: GT-I9505 (Probably LTE version)

I9505XXALL1/I9505OXAALL1/I9505XXALK7

As per other reports doing the rounds in the tech world, Samsung Galaxy S4 will most likely feature an unbreakable, flexible display. The smartphone is rumored to be powered by Exynos 5450 chipset with a quad-core Cortex-A15 processor. It will likely have a 13-megapixel camera.