I'm going out on a limb, and based on your description of the guitar, and my bizarre theory, say that this is a 1948-1949 model.
My FON also has an 8 in it, and that is quite blurred. Although that 3 can be more clearly read, I can also see how your first number could be 3 rather than 8, just from examining the shape of the 3 in the FON of my J-45, and knowing how it can be blurred when there is too much ink on the stamp. I have a J-45 from the same general late-40's period, and it has a 3 as part of the FON. I have never seen a picture of the actual type of ink stamp that Gibson used, which could help to determine if this is a plausible theory. My first thought was that the batch and rack number had somehow been reversed, but that could only work if the first two digits are 35 rather than 85, since the rack number is usually 40 or less.
I assume that it has LG 1 stamped on the inside back centerline, since you have identified the model. A picture of the front of the guitar would be helpful.
