Here I show how to decode your Master Lock 1588D magnifying dial locker lock in case you have lost or forgotten your combination code.
I hadn't tried this model before & I had to figure it out.

Method:::

To find the first number, you should turn it several times to the left (counter clockwise) while putting gentle tension on the shackle and slowly increase the tension until one number seems harder to turn past than the rest. Add 7 onto that position to get the 1st number!

To find the third number, pull up on the shackle with medium / hard tension, and test all the "gates" and look for the one with the largest movement in its gate. That is the 3rd number!

To find the second number, don't pull up on the shackle, and turn several times (full turns) to the right (clockwise) and stop on your first number, then turn one full turn left (counter clockwise) until you get to the first number again and keep going to your second number we don't know what it is but we'll test each number keep turning left to the next number and then turn right (clockwise) to the 3rd number, pull up on the shackle, and if it doesn't open then turn left to the next 2nd number try & back to the 3rd number, pull up to see if it opens. Repeat until the lock opens.

More details (and tips & tricks) are in the video.

Important when you're finding the 2nd number, as you increase the 2nd position tries, you might go past the 3rd number position, in which case you only have to turn the dial left a little bit to get to the 3rd number (*not* all the way around!).

It can take a while, but if you follow the instructions in the video you should be able to crack it.

00:00 Intro
01:18 Attempt to find the 1st number (failure)
02:33 Find the 3rd number (success)
05:11 Another attempt to find the 1st number (failure)
06:42 Yet another attempt to find the 1st number (success)
08:08 Attempt to find the 2nd number (failure)
11:33 Another attempt to find the 2nd number (success)
12:09 Open!