Within a day of the October 16 opening up of the pre-orders for Microsoft `Surface' Windows RT tablet, the company has revealed that it has run out of its initial supply of the low-end, Touch Cover-less, 32GB model of Surface RT.

Going by the information shared by Microsoft on the Surface pre-order page, the first supply lot of the $500-priced version of the tablet has exhausted; and the device is now backordered by three weeks. The page clearly mentions that the lowest-priced Surface RT model - which comes without the cover-cum-keyboard - will ship "within three weeks."

However, the page also mentions alongside that the delivery date of the other two high-end Surface RT tablet versions - both of which come packaged with a black-colored Touch Cover - will still be October 26.

Though some industry watchers find it quite surprising that Microsoft has exhausted the initial supply of that Surface RT version which ships without the much-talked about Touch Cover - the biggest selling point of the tablet -, Microsoft itself has refrained from making any official disclosure about exact number of $500 Surface RT units it had made available for pre-order.

About the lowest-priced Surface RT tablet becoming the first version of the tablet to be sold out, a Microsoft spokesperson merely said, "No numbers to share, the $499 one is now on backorder;" and added: "That means that SKU is out but all three SKUs will be ready for launch day."