What does "nac" stand for at the bottom left corner under a picture?

Question

It is a picture by AJ Casson 1958 "Mist Rain and Sun"

Answer 1

I found this:
"Northland Art Company" (NAC) is a distributor of limited edition prints, which are available through Authorized NAC Dealers across Canada. The NAC brand makes artwork available to the consumer at exceptional prices without sacrificing quality. For an Authorized NAC Dealer nearest you, contact Northland Art Company at [phone]; toll free at 1-866-208-7244, or email us at [e-mail]
They also make reference to A.J. Casson prints as well. I hope that this helps!
http://www.northlandart.com/htmfiles/faq.html
http://www.northlandart.com/news_pr/jun10b-04_pr.html

Answer 2

Aj Casson Prints