Many clock frames, as below, show a pattern of repeated indentations covering most of the surface of the frame. The still is from a video showing the behaviour of the clockwork which is not relevant.

Partial view of clock frame

I have tried to search for an explanation and hoping an AI would know received the commentary that the marks were possibly aesthetic, provided improved grip or were a manufacturing artifact. As none of these seem likely, I asked for an appropriate StackExchange forum and was suggested either "Clockmaking & Horology Stack Exchange" or "Clocks & Watches Stack Exchange", neither of which exists. This forum seems to be the closest in intent.

As I have seen this effect on clocks mostly from earlier in the 20th century, I don't believe that they are tool marks from rollers moving material around in a CNC cutter of some sort. There is also the fact that the indentations do not cover the entire surface making the clamping hypothesis unlikely.

These marks are clearly not the same as the circular overlapping polishing marks used in the finishing of exterior visible surfaces and the introduction of features this small seem unlikely to be a work hardening exercise. The look to be too regular to be hammered individually into the plates. I don't believe the process is brass-specific - this may be self-selecting from the use of these frames.

Is there any consensus on the purpose and mechanism of application of this interesting finish? Is it still in use in current processes?

Further examples showing broader adoption of the technique, but with no clear orignial source:

  • 4
    This little experiment should teach you that AI (expecially current chatbots) don't actually know what they are saying. They just string the most probable words together to create some text, but they have absolutely no knowledge about anything they write about. You cannot trust any information any AI gives you.
    – Elmy
    Commented Aug 29, 2023 at 20:04
  • 1
    Their strong preference to produce output rather than disclaim knowledge is a large driver to their less than satisfactory performance. I was just impressed that it came up with two possible names and both had nothing to do with reality. I only asked it after I was unable to find a reasonable venue for the question in the first place.
    – Pekka
    Commented Aug 29, 2023 at 20:56
  • I've seen something similar on other things, but can't recall what. Maybe if I could remember it would give a hint
    – Chris H
    Commented Aug 30, 2023 at 10:36
  • AI is a misnomer. There is no intelligence, only the parroting of data patterns.
    – rebusB
    Commented Sep 1, 2023 at 16:05
  • 1
    @Joachim I've added links to additional examples showing this was across a broader geographical area and over some time. The finish seems to be limited to mechanisms that were designed for boxing to hide this less than desirable finish. It clearly not very common as I had to scan through several hundred images for these.
    – Pekka
    Commented Sep 2, 2023 at 21:21

2 Answers 2


It looks like the brass plate serves as a sort of breadboard for the clock structure and components. All of the pieces attached line up with the holes, as well as one end of the assembly itself.

So the holes would serve time saving and organizational functions. They allow for a gridded layout of the components and provide tap points for drilling out larger holes for screws to attach to.

  • 1
    I think so too. These brass boards may have been manufactured by different companies to cater to the needs of a range of clockmakers/clockmaking factories (the images of boards added later are different, but the concept is the same, indicating multiple factories working with the same universal or generalized 'blueprint' board).
    – Joachim
    Commented Sep 5, 2023 at 8:29

An explanation for the hole pattern appears in this Amazon watch repair product:

enter image description here

In any case, if I were a watchmaker, it would be very useful to have a basic grid to work on, a visual aid to place elements in the correct place.

  • 3
    I fail to understand how a plate with holes explains the indentations in clock frames. If nothing else, the product you show as radially placed holes and the marks in the image are clearly on a regular square grid.
    – Pekka
    Commented Aug 30, 2023 at 10:31

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .