I remember the term Merlin, vaguely, but never had one. I do remember the whole thing about slicing the strips lengthwise in half; there were even companies that sold devices to do that, though the manufacturers warned not to.
Of course, when we moved away from visual reading to the meters, we couldn't do that anymore.
Here's an image of the color-chart that we used to compare. (Thanks, Kerri, from sixuntilme.com!) If we were running high, we had to try to guess where we fell on the color-chart between 240 and 400!