You need one of these https://www.harborfreight.com/snap-ring-pliers-with-interchangeable-heads-63845.html or you get creative with a binder clip’s clip.
I just use tweezers. Haven’t had a problem removing the tailcap retaining ring in any FW3 series light yet.
This is of course a very silly remark but: did you try to turn it in the right direction.
My FW3A has only one righthand (clockwise) thread.
That means the retaining ring uses the same thread as the body/tube.
So turn it counterclockwise to loosen it.
And it is essentially to use two pins when tightening or loosen it.
That can be done by a set of needle nose pliers. I use two SS nails, always does the trick.
$3.00 (small) Needle Nose Plier’s…………… Righty Tighty-Lefty Loosy……
This helps immensely…I have some needle nosers so I’ll give it a try today.
Also, the thin silicone gasket on the tail side was ripped and fell out when I opened the tail…should I be worried about that at all?
Thanks again guys!
When you say “thin silicone gasket”, my guess is you’re referring to the thin white o-ring above the clip. That o-ring isn’t needed for waterproofing and not having it won’t compromise the light. All it does is prevent the clip from rotating when the light is sealed.
If you don’t want the clip to rotate, you could try removing the black inner tube from inside the body tube. They usually come with a second white o-ring intended to center the tube, but in my experience it isn’t really necessary. You could remove that second white o-ring and place it just about the clip (between the clip and the black o-ring).
Mine didn’t come with any extra white/translucent o-rings (just 2 black o-rings) but I’m sure I’ll figure it out.
Thanks
I just realized, from your images, that maybe you misread what I meant with the retaining ring…it has nothing to do with the 2 circular holes on the board for twisting removal or the board itself…but an actual black metal retaining ring on the whole board itself…most likely Lumintop’s attempt at keeping the coil straight from a lot of prior complaints. Here is image I lifted from another flashoholic that spotted it as an update.
thank you
The same retaining ring on my FW3A is now also too tight to move; I have tried tweezers and snap-ring pliers without success.
Exactly…it’s insanely tight and I don’t want to scrape the sidewalls with too much force and thrash the threads. I ordered a Snap Ring Set from Amazon Prime but the virus has slowed down all shipping so I’ll report when I get everything. Otherwise, if I can’t get it to work I’ll have a nice Cyan Glow Button for Sale Cheap 
I have tried Channellock 926 and 927; if I apply too much force, the tips slip out of and abrade the notch in the retaining ring.
I’m in SG/Alhambra I’ll loosen it for you with my snap ring pliers if you stay 6ft away from me.
Ha…really! Deal! I’ll PM you. 
If you’re using excessive force with the pliers in the notches then you might well be chewing up the threads and locking the retainer in position.
I noticed that as well…went in between the indents with a little force and a tiny bit of metal dust scraped out so I stopped until I have the right tools ordered.
Yeah let me know, mostly free on the weekend with this quarantine going on. Let me know if you want the o-ring mod also, I can bring one.
awesome, just PMd you…
Just tried to remove mine from my FW3C and it is very tight, like the others I don’t want anything slipping and ruining the soft copper threads, I have pliers (like too many sets) ring pliers etc, none of them will budge it, at least at a force I’m happy with trying, I can see me having to make a specific steel tool eventually……
I don’t suppose anyone has a tailcap button out who can measure all the sizes (everything, even the indent in the back, depth etc) so I can make one first, then deal with the ring lol!
Would appreciate it if so, in mm! 
I’ve always used the handles off of a binder clip, never had any issues.
Yes I know that’s the head but it works the same.
Or just get this lol.
Nice! I’ll try it.