I'd test and see if it's a factory code first. Blank Registration made a worksheet for factory code Speed Dials (Google Doc), and a companion video showing how to use it. It'll take <10 minutes to check if it's a factory code.
If it's not a factory code, try using a couple experimental decoding wizards:
Yehonatan Knoll is the inventor of a novel combination lock which uses four rotatable disks that are spun by a control piece moving in up, down, left and right directions. The lock remains closed until a true gate on each disk is aligned with a windmill-style fence, at which point the shackle can be opened.
Manufactured locks were available directly as the Knollan Saly Dance (see the marketing/investment brochure!,) or more commonly, produced under the Master Lock brand name – Master Lock Speed Dial/1500iD/ONE. As of October 2022, all lock manufacturers seem to have discontinued production of Knollan-style locks.
In 2008, Michael Huebler (mh) extensively researched this locking mechanism, writing a wonderful analytical paper (PDF)2 and creating a visualizer for the internals, written in Flash ActionScript. For current usage, there is an HTML5 <canvas> adaptation of mh's visualizer with additional features for lock research.
mh, Blank Registration and myself have written about a number of techniques to decode the Master Lock Speed Dial, with or without computer assistance. I'd recommend checking out the LP101 thread for more info. The Knollan brand locks, because of their false gates, are only known to be decodable with tooling.
Progress is slow but I am attempting to create interactive decoding wizards:
Blank Registration has developed a keyspace reduction technique for the Master Lock Speed Dial (video and writeup) which reduces brute-force search from 7501 total combinations to at most 75. There is also a computer assistant to more easily implement the technique.
The Knollan, which contains two false gates on each disk, remains elusive :) Please join in the quest!