Printing Types

Hello! 

I don't really get the various reference numbers in this banknote.  Can someone explain the difference in printing technique?

I'll be attaching photos of my note in case someone might help me here. Thanks!!

It has an X prefix, shouldn't it be P#122s then?

I also think it is hard to spot the difference on these two notes.

According to various sources, the P#122a has an obverse which is engraved/Intaglio printed and the reverse is lithographed/offset printed.

The P#122b has both sides lithographed.

I got one of each of these notes and I scanned them at a high resolution, just the obverse side that has the different printing techniques.

Here is the same portion of each note, on the left is the P#122a and on the right is the P#122b:

The difference that I can see is that the P#122a note (engraved/Intaglio) has more variation in ink density. What I mean is, it can have one filled shape with a dark red center that gradually gets lighter towards the edge.

On the P#122b note there is not that degree of variation in ink density. But…the edges look cleaner to me.

What I don't know, is how someone can work out whether a note was engraved or lithographed in circumstances where they have never seen or researched the note before and have only the one note to examine.

If someone has a reliable way to determine that, I would like to know!

Technically intaglio should be slightly raised, it should have a slight profile when held at an angle, or you can feel it (obviously not advisable for UNC notes and circulated notes can be smoothed down). The lines should bleed a bit more then on engraved ones but on the provided examples there is quite a bit of bleed on both (alas on different locations).

Theoretically there should be a way to tell the difference through the prefix letters. Does anyone have any information about what prefixes were used with each printing type? 
 

I have what i think are both versions with one note having a “low” prefix and the other a ”high” prefix. There seems to be big differences in the colors used on the dam. Then again quality control on Indonesian notes back then was not a big deal. I would love to know how to differentiate these notes too.

Idolenz

Technically intaglio should be slightly raised, it should have a slight profile when held at an angle, or you can feel it (obviously not advisable for UNC notes and circulated notes can be smoothed down). The lines should bleed a bit more then on engraved ones but on the provided examples there is quite a bit of bleed on both (alas on different locations).

The bleed to me is much more obvious on the engraved note. Look what happens if you cycle the images, it is really clear then:

There is also the position of the circle element on the left that might indicate the different plates. If the technique and the position where it touches the design element are linked.

Idolenz

There is also the position of the circle element on the left that might indicate the different plates. If the technique and the position where it touches the design element are linked.

This looks like a good way to differentiate the two! Hoping that we can see other examples for comparison :)