Thai serial number error possible

I have been doing serial number studies to try and figure out how many notes have been printed of recent P types of Thai banknotes and have uncovered a small mystery.

I have a P-120 with original signatures, so P-120a, but.......

P-120 (banknote.ws)

Now P-120a used letter codes A/ก, B/ช, and a few runs of C/ค. Between 200-300 million notes.
P-120b started somewhere between 4 and 9C/ค and stopped before the J/ร code. Less than 600 million banknotes.
I know that P-120c starts with or prior to prefix code J/ร. After the run of the 9 English letters (A,B,C,D,E,F,G,H,J), the prefix codes start back with A but the Thai letter is shifted. In the second run prefixes start with A/ร.

Now the mystery. I have a note with a signature set that belongs to P-120a but the prefix code (A/ร)belongs to P-120c. Is anyone aware of errors with Thai serial numbers?

I am aware of other countries having mismatched serial numbers when a wheel gets stuck but I am wondering if on my note I have a wrong Thai letter because a wheel turned when it was not supposed to.

Any info to help me with this mystery would be greatly appreciated.


If anyone would love detailed information on how Thai serial numbers work, let me know through PM and I can send you a pretty thorough guide on Thai serial numbers.

Its common in some countries to follow up prefix in different series and mix them sometimes.. e.g
P120a - Prefix A, B, C
P120b - Prefix C, D, E
P120c - Prefix F G
P120d - Prefix A, B

The above is just an example... so its not exact information, but just more like an explanation of how some banks follow serial numbers in some cases.
1. you can see that the prefix C is repeated in type a and type b... that happens if they will like to continue with the serial number... lets say they printed type a up to C3499999 and then continue on type b with C3500000.

2. You can see they don't repeat Prefix E from type b to type c it could be that they printed type b Prefix E up to E9999999 or that they just wanted to continue with the letter in the next type.

3. You can notice that in type d they started with Prefix A again... this could happen because all type a,b,c,d are different dates, and/or different printers (Contracts awarded to a different company).

It's really a very interesting topic to analyze (and a very confusing one). I am not an expert on Thai Prefix nomenclature or whatever its called, but perhaps there is a channel on the central bank that could explain you how they program the sequence. or specialized book that record this... and last but not least and paper money society in bangkok that could share more on this...

Citeer: "JustforFun"​Its common in some countries to follow up prefix in different series and mix them sometimes.. e.g
​P120a - Prefix A, B, C
​P120b - Prefix C, D, E
​P120c - Prefix F G
​P120d - Prefix A, B
​
​The above is just an example... so its not exact information, but just more like an explanation of how some banks follow serial numbers in some cases.
​1. you can see that the prefix C is repeated in type a and type b... that happens if they will like to continue with the serial number... lets say they printed type a up to C3499999 and then continue on type b with C3500000.
​
​2. You can see they don't repeat Prefix E from type b to type c it could be that they printed type b Prefix E up to E9999999 or that they just wanted to continue with the letter in the next type.
​
​3. You can notice that in type d they started with Prefix A again... this could happen because all type a,b,c,d are different dates, and/or different printers (Contracts awarded to a different company).
​
​It's really a very interesting topic to analyze (and a very confusing one). I am not an expert on Thai Prefix nomenclature or whatever its called, but perhaps there is a channel on the central bank that could explain you how they program the sequence. or specialized book that record this... and last but not least and paper money society in bangkok that could share more on this...
​
​

​I am very familiar with how the Thai serial number system works. Thailand has a very unique system with serial numbers. There are 9 English letters and 9 Thai letters used. Each English letter is paired with a Thai letter and then after the initial 9 combinations, the Thai letters are shifted one space against the English letters. The combinations continued in a set pattern and continues through until the major design is changed. There are literally 81 combinations that can be used with this scheme, however Thailand has never come close to using them up. Each combination produces 100,000,000 notes. In total it could reach 81x100,000,000 notes.

The first 9 combinations are A/ก, B/ช, C/ค, D/ง, E/จ, F/ฉ, G/ด, H/ท, J/ร (I is not used)
The 2nd 9 combinations are A/ร, B/ก, C/ช, D/ค, E/ง, F/จ, G/ฉ, H/ด, J/ท
The third 9 start with A/ท, and so on

120a used A/ก, B/ช and some of C/ค.
120c started with and used J/ร, A/ร, B/ก, C/ช.

The signature set I have in question should be one of A/ก, B/ช, C/ค (120a) but it is A/ร which belongs to 120c. This is why I asked if anyone knew of Thai serial numbers errors. I did find one error where the same serial number is on two different notes. It happened with the 50 baht polymer note they made.

I will look into a banknote society in Bangkok.