There are at least three different versions of the UK101 motherboard.
The first version of the motherboard that was available for sale is distinguished by the lack of the green solder mask.
The second, and most popular, version of the motherboard has a green solder mask on both sides of the board. It is different from the third version by not having the word "EPROM" on the lower left of the board.
The third version of the motherboard is distinguished by the word "EPROM" appearing in the top copper layer in the lower left corner. It is assumed that this board has the correct chip select lines for EPROM versions of all of the ROM chips.