As Andrew says, the dimples are for tightening! I've just been down to my boat and had a look. There are two little insets opposite each other so one can apply an even force. A hammer may help - I'd use a wooden drift between the winch top and the hammer! and not hammer directly onto the winch cover. See if you can get some penetrating oil (eg, Plus Gas) under the cap and leave overnight. WD 40 isn't penetrating oil - it's what is says on the tin - /W/ater /D/ispersant (I wonder what happened to numbers 1-39?).
I serviced mine when I bought Nosey and guess it's time to do it again. I washed the pieces in paraffin, more oily than petrol, and then sparingly applied Lewmar's winch grease as in the directions. Salt will collect on excess grease. I believe that giving the winches a good hosing with fresh water helps keep the salt and grit out. Which reminds me, do order a winch overhaul kit, which will contain spare springs etc. Try an online search for it. If no luck, email me and I'll see if I can find my source.
John
<i>Nosey</i> Parker 326-26