About 2 weeks ago I switched watches to make a run to Lowes with my neighbor to collect supplies to do a project I am helping me with. I forget which watch I took off but I put on my Black Bay since I am less concerned if it got scratched loading and unloading lumber. I set it to within a minute and ran out the door. After the trip, some planning and a couple of beers I walked home, a total of about 4 hours and when I sat down I noticed the watch was near 5 minutes fast, I figured I just set it 5 minutes fast as I have been known to do. I switched watches but wound the Black Bay up and sure enough the next day it was almost 30 minutes fast. Since it was well into the holiday busy season instead of running to my AD I figured it was time to get the demagnetizing supplies. AFAIK I have ever magnetized a watch and have no idea how or if this one got magnetized.
So after a couple of days of procrastination I hit up eBay on the 23rd and ordered a decent compass and the cheapo demagnetizer that "everyone" uses. Total shipped for both was $15.49 and I made sure they both shipped from the US (mainly to get them faster), I could have saved 6-7 bucks if I went the full China route and got one of the .99 compasses but I would have had to wait a couple of weeks. In any event they shipped on the 24th, got them yesterday. I checked and verified a very slight magnetic field with the compass and demagged the watch. Just held it to the demag for a second and slowly pulled pulled it out to arms reach and let go of the button. Verified with the compass the field was gone and now 24hrs later the Black Bay is +3 seconds, just like before.
Really nice to be able diagnose and remedy this for ~$15 and although my AD will do it for free it either saves a 1 hour trip or prevents me from waiting until I am in the area. Pretty nice for less than the cost of a quality spring bar tool.