Naw, we should have used 420 to ensure we can also cleanly divide by 7.
Maybe even 1260 so we can fit a division by 9 in there (420 already has 3 as a prime factor, so only need to go 420 x 3 to get a clean division by 9). I suggest ending there since we could divide by everything up to our number of fingers.
Using your modified Babylonian system, I think you can actually make it to 168.
Using one hand for lower digit and other for higher digit, you can effectively count in base 13 on the higher digit hand to 158 (13 x 12). But you can then count an additional 12 on the lower digit hand leaving you with 158 + 12 => 168.
There's probably a nice graphic online, but I'm too lazy to find it. Lol, so instead I'll try to type out an explanation (apologies if it feels somewhat mansplainy)
So you seem to get how to count to 12 on one hand. Once you reach twelve, your next digit would be 13 (0 on one hand, 1 on the other). Then you count up again in the first hand to twelve (for 13-25), then go to the position of two on the other hand (and zero on the first) for 26.
Continuing in this way, you'd max out the other hand at 156 (12 x 13 = 156, with the other hand pointing at the 12 position). From there, you can count out another 12 on the first hand getting you to 156 + 12 = 168 total (leaving you one short of 169 = 13 x 13, as is typical of these kind of digit counting problems).
Edit: just did it in my own fingers as a proof and yeah, you can get to 168. Not in a good place to take a video or whatever to post, but would if I could.
More significant hand maxes at 12 * 12 = 144, plus 12 on less significant gets me to 12 * 13 = 156, how are you getting the 13 on more significant one?
So you can indicate zero on your left hand by not touching your thumb to your hand at all.
Then you indicate 1 by touching your left thumb to the first section of your left index finger. You count along the sections of your fingers until you reach the end of that finger (should be 3), then moving to the next finger, with the first section of your middle finger being 4. Moving in this way, when you reach the the last section of pinky, you should be at 12.
Then you lift your thumb off your left hand completely as you touch your right thumb to the first section of your right index finger. You have indicated 0 on your left hand and 1 on your right. This is the equivalent to 13.
Continuing this way, you can indicate the multiples of 13 (13, 26, 39, etc) as the sections on your right hand (with 0 indicated on the left hand). When you reach the last section on your pinky with your right hand, you have counted to 156. (And then you can count an additional 12, but that seems to be something we're clear on).
I'm actually unclear how you'd get multiples of 12 out of this? Do you skip a section of a finger? Or, like, as you touch the last section of your first pinky, is that when you touch the first section of your other index finger? That latter option feel redundant, and so I'm not clear why that approach would be advantageous?
Edit: trying clarify by indicating left and right hand (as I count with this method) instead of 'first" and "other" hand (to be more general to how others might do this).
Both of my hands have 12 segments, so 12 segments * base 12 = 144. If I add the less significant hand, I get 12 * 12 + 12 =156. Where is the thirteenth segment of the more significant hand?
Edit: WAIT, you are counting in base 13! Now everything makes sense!
12 segments * base 13 + 12 = 168
I think your hands should at least be flexible enough for 4 & 132 (its one (4) or booth (4+128) middlefingers)
when i count with binary i mostly just "drag" the finger a bit forward instead of complely folding it.
Its more comfortable and faster, i really just need to understand it myself what is on or off.
I've always has difficulty with it, largely since I only learned my times tables to 12 as a kid (American education, amirite?). I so rarely count in my fingers beyond 10 that it hasn't been useful to memorize that next set.