Nobody else has responded yet, so here's my 10 cents...
I initially figured that you were right in assuming some sort of PWM driver chip until I did a bit of digging in the net.
I searched for "led spotlight driver circuits" "led power driver circuits" & checked out the images containing ICs with 8 pins..
I was surprised (& somewhat dismayed ;^) ) at the huge variety of different driver applications and circuits....
In addition to PWM drivers, there are current sense drivers, buck drivers, array drivers etc. etc. etc...
After many fruitless red herrings I DID find a circuit that at least seems to use the same pins of an 8 pin IC in a similar
Check out: http://www.diodes.com/_files/product_ap ... N75_r0.pdf
This is an "AL9910 high power factor buck LED driver"
The circuit in the green box on page 1 looks VERY similar to your circuit.
If your circuit is also a buck converter then this would also explain why the circuit seems a bit wierd & not easy to understand..
I dunno if this will help, but this is the only circuit I found that is close to your device & the "high power factor 13W LED lamp"
application also matches your device....
Just in case you don't already know them, here are a few tricks for reading illegible/invisible IC markings..
1/ Use a bright light and magnifying glass to examine the chip at all possible angles (especially at very low angles, almost from the side)
2/ Repeat step 1/ with a UV light source
3/ Wet your finger & rub a thin film of moisture on the chip & repeat step 1/ as it dries
4/ Spray a thin film of contact cleaner on the chip & repeat step 1/ as it evaporates
5/ Spray a thin film of freeze spray on the chip & repeat step 1/
6/ Cool (dont freeze!) the pcb in a fridge, then breathe on the chip & repeat step 1/
7/ Desolder the sucker & look underneath
If you have'nt already tried all the above then give it a go.
I have often been amazed how "invisible" markings can be revealed by the above methods.
I hope this helps you with your puzzle.
Irrelevant mythological quote: "Be yourself, unless you can be Loki, then be Loki"