I also have never heard of 24LS256 but maybe it's a code used by some small fabrication company. I would guess it would be the same specificaton as 24LC256 which is commonly available.
Are you sure it's an EEPROM? There is a 74LS256 but that's a TTL latch device.
Interesting, I actually have a few of these in the parts bin. I always thought they were cheap Chinese knockoffs with a slight misspelling. I still occasionally see large lots of the 24LS256 offered for sale on the wholesale Chinese semiconductor marketplaces.
I think an 'LS' (= bipolar Low power Shottky) version of such a dense memory is unlikely but smaller manufacturers often change the letters to 'customize' a standard part so it sound like their proprietary design. I would guess the 'LC' data sheet covered this device.