Does anyone know what the letter printed on the battery means ?, some sort of grading ?. The one in the picture here has the letter “C” printed on it, the ones I have are marked “B” and “C”
That letter is the cell grade. It is not clear how Panasonic/Sanyo grade the cell, but they do state in the specification that cells must be of the same grade when they are used in series.
Thanks for the reply, and welcome to BLF 
Here are the discharge capacity measured with my Xtar Dragon VP4 Plus. The current batch from Illumn.com is the best batch I’ve seen.
Bought from Liionwholesale.com in January 2017
3375, 3557, 3479, 3391 mah
Bought from Vacell directly in November 2018
3480, 3552, 3502, 3467 mah
Bought from Illumn.com in August 2019
3570, 3584, 3631, 3549, 3561, 3600, 3611, 3540 mah
Samsung 36G for comparison
3454, 3385, 3427, 3463, 3328 mah
Still my favorite do anything cell.
Time to bring it alive after 3 Plus years! I have the unprotected button top version. Black Friday sale.
I don’t need to use them now. So the question is if they were to be stored for 2 years and possibly more should I take them out of storage after one year and charge them and then put them back in storage? Or is it okay to leave them at like 3.55/ 3.6 Volts for 2 years?
Thx
Thanks for the numbers. That Dragon seems a bit High. HKJ got 3264 milliamp hours.
Just bought four more from Black Friday sale from Liion wholesale. Unprotected button tops. I’ll give my Opus results this evening when they’re done. I suspect they’ll be around 3400 something my Opus is pretty close to HJK numbers.
They’re very good batteries! Still the best for capacity and discharge CDR. Depending on your charger termination voltage, expect around 3200-3300 mAh
HKJ got 3264mAh @ 1 Amp.
My 4 slot median at 1 Amp is 3290mAh. 
I found divergent information on this, with different documents (both from Panasonic) pointing to 4.0 and 4.5 hours.
Also, what about charge termination current? @HKJ does not mention it and neither does the datasheet he seems to have quoted from, but the other Panasonic document I found mentions it explicitly as 67mA.
More details in the topic I just posted: Sanyo/Panasonic NCR18650GA: recommended MC3000 parameters for charging/discharging in order to reach nominal capacity?