Don't beat yourself up on that. Different blades can be ground at different angles, no real right or wrong. I grind mine with a 4 1/2'' angle grinder and don't really pay attention to the angle, just so it's sharp at the edge
I just ordered the 5005 model with adjustable angles. I also ordered TECOMEC wall mounted precision blade balancer 42-047. It it is the exact same balancer as the Oregon but I got it for $20 to $40 less than the Oregon. Tecomec, in Italy, makes them for Oregon and Oregon put their name and price on it.
I have two of the All Americans. I first ordered the standard one to quickly find out some of my blades are on far different angles when new. And, I have some left hand blades. So I ordered the model that both allows angle adjustment and right or left hand use. Both are great, but I have no real use for the basic one. I balance on a motorcycle wheel balancer, works great.
I don't need a machine. All I need is a chair with the blade laying extended off my leg and my Makita Rt angle grinder. Free hand is fun. My pocket knife blade centered in the hole for balancing does that just fine.