I’m in a somewhat similar situation as you, @David49, though different, as well. When I was diagnosed, I was trim and active with a reasonably healthy diet. I had maintained weight/diet/activity level for close to a decade prior to Dx. I was also asymptomatic at the time. My doctor “didn’t believe” I could be diabetic, but, due to age, diagnosed me as “Type 2.” Metformin had only minor affect on my BG (mostly reducing FBG by a little), so I was quickly put on one, then two additional medications. ALL of the orals had “some” affect, but also caused some unusual and intolerable side effects, so by the fourth month after Dx, I was taken off all T2 medication and put on insulin - and referred to an endocrinologist. C-peptide, insulin and anti-GAD65 were tested, though postprandial, rather than fasting. C-peptide and insulin were “normal” (for fasting), but the antibodies test was negative. With those results, the endo confirmed “Type 2” and proceeded to help me titrate insulin dosing. Only GAD antibodies were tested.
Problem is that over time, my c-peptide was re-tested several times (as was insulin) – these times, fasting. Each time, c-peptide tested lower than ever before, and always well below the “normal” reference range. Throughout all this time, I managed to achieve and maintain reasonably tight glucose control, with A1c’s in the 4.9-5.6 range (mostly on the low end of that range). Diet and exercise have helped me, but, in my case, not enough without taking insulin as well.
LAst month, after the most recent c-peptide came in at 0.2, (and perhaps, together with a low CRP, showing none of the anticipated inflammation of T2?), my endo declared me to be “Type 1”.
To be honest, I don’t know what to really think. Does it make a difference for me? I don’t know. I’m already taking full basal/bolus insulin. I have very little insulin resistance, taking a total daily dose of around 41U. Already use a pump and CGM. I take no other medications for any condition. I have made some additional diet and exercise changes over the course of the last several years – all of which are healthy habits for anyone, diabetic or not, so clearly beneficial. Insurance might be “happier” or easier to work with with a Type 1 diagnosis, but otherwise, what does it change for me?
There was a British study published last month that indicated that the incidence of Type 1 remains consistent at any age, and that 20% of people with Type 1 present without testing positive for any of the known “Type 1 antibodies.” They used some kind of genetic markers for identification, I believe. They concluded that neither age, nor anti-GAD65 testing is sufficient to identify Type 1 vs. Type 2, though, as they found no incidence of negative consequences of misdiagnosis as Type 2 (people who needed it, were 100% likely to be on insulin), I don’t believe there were any immediate action points from the study.
You, me, @David_dns, maybe @Brian_BSC and several others – we need our own special designation. I usually call myself “Type Weird” - fits my personality, at least, and maybe my condition as well! 
It might be useful in figuring out what my son’s risk is, but I figure we’ll have to watch him close regardless.