On a recent "American" board , made in China, so no warning legends of PbF .
Don't know what its called, the sort of conformal coating final process at
the pcb production phase is a staining coat , usually green these days.
White rings showing around the solder pads after soldering may show elevated
soldering temperature has been used or wrong composite material body ,
showing rings of plain white polyester+fibre board . The green staining
having melded into the plastic or evaporated.

From UL 6 digit E number and board type this is designated 260 deg C / 10
second solder dwell ( for conventional soldering) rather than 270 deg / 10
second dwell of proper made for PbF pcb boards.

If anyone knows the significance of 288 degree C / 8 second soldering dwell
time pcb +soldering rating in comparison to 260/10 and 270/10, I would be
interested to hear.

IPC-TM-650 Test Method 2.4.24.1. would seem to be the test, should anyone be
interested
Time to Delamination (TMA Method)
10 second solder float
http://www.matrixusa.us/pdfs/solutio...ree_Basics.pdf
http://www.ipc.org/4.0_Knowledge/4.1...t/2.4.24.1.pdf

Wrong tests , more likely this test, as seconds not minutes, peel strength
not delamination

Solder float peel strength: (no change after 288C/10 sec)
eg
http://www3.uic.com/wcms/images2.nsf...mage_Test_Plan.
pdf/$File/2006_PCB_Damage_Test_Plan.pdf

So I reckon the ul.com pcb classification is this test
http://www.ipc.org/4.0_Knowledge/4.1...t/2.4.8.3a.pdf
with 10 second solder float for the heating stage
Then passing 260 degree C for leaded solder use
270 deg C for PbF
288 deg C for high spec like polyimide/ N7000-1 /Pyralux