I’ve got a Greenbrier civvy MA-1, runs slightly bigger than standard Alpha, materials not quite as robust as USA Alpha jackets IMHO and lighter weight..which has it’s advantages in milder weather. Service issue Greenbrier I’ve always found to be of very good quality.
Probably the easier way to tell is the weight of the jacket and the tags. This is the civilian version which is lighter weight with a commercial tag . The military ones have white (I think) tags with all of the contract information you would normally find on a military jacket . The color difference in the photos is a result of interior lighting .