I'm very confident I've solved the riddle around Spörkes. It appears to be German Sparren (also Sparre, Sparr, Sporr,, etc.). It's a very common word that describes the roof construction of a house. This would suggest that Spörkes means something like "little roof", which very naturally fits modern German "Dach" (roof) for circumflex (and english "roof" beeing used in the same way, iirc). Even better, dialects use a diminutive for a roof in the meaning of a written character, e.g. Bavarian "Dachl".
EDIT: I found proof (in the DWB) for the use of Sparren as word for the symbol. Since the middle ages(?), Sparren is used in heraldics for two beams that make a roof shape:
https://en.wikipedia.org/wiki/Chevron_( ... )#Heraldry
This would suggest that Spörkes was written as Λ, while half Krütskes was V and Krüstes is X. Assuming Nothringskes is indeed a circle, this would roughly lead to this number system:
1 I
2 II
3 III
4 O, oo, 8 (?)
5 V
6 Λ
7 Λ I
8 Λ II
9 Λ III
10 X
11 X I
20 XX
EDIT: I admit that a roof structure might also be symbolized by a comb shape, but a Λ seemed easier.
A few little remarks regarding Nothringskes: The DWB suggests that prior to meaning "need", "requirement", "emergency", german Not universally meant "pressure", "compression", "urge to squeeze together". Taking this into account, Nothringskes would translate as "squeezed little circles", which might be an 8, an infiity symbol (oo), or something like overlapping circles.
EDIT:
Looking at it again, it seems more likely, that the system is slightly more sophisticated:
The number 1000 is called Krütskes Uhr, literally "ten hundred", suggesting, that is was not written as DDDDDDDDDD (using D as a plaecholder for half Uhr), but instead XD. (Why does it suggest that? Because the names describe symbols, not numbers.)
Thus meaning that a smaller number before a bigger digit multiplies it. For example 70 might actually be ΛIX, "Spörkes-un-Ehn Krütskes".
The Parz Spörkes (20) that I wrote above would then be IIX.
EDIT: Some thoughts regarding Uhr and holf Uhr: Above I wondered, if holf Uhr might be D and Uhr is (|). This might be even more likely, if they used romand numerals and reassigned |) "500" to 50 and (|) "1000" to 100.