By what method is this type HS done

This is a very quick photo of the head of a cadmium-plated steel cased L/60 Bofors.

The very shallow headstamp looks like it was applied by an electro-pencil, as it is a series of impressed dots, but that can’t be, unless it computer driven & so to be able to do the quantity and quality need for this application.

So a name for this method of headstamping would be appreciated and perhaps a simple explanation?

Maybe laser-engrave headstamp.


Brian, looking back at when these steel cases were made I think laser marking in this quality was technically not possible (or done at all).

Pete, a better image of the stencilling would be helpfull.

“Electrical erosion”

Pete, Any chance of a better picture as yours does not enlarge very well at all.

The only method like this that I have seen was vibro-engraving and don’t think this was used on cases but it has a very distinct pattern but without being mechanised is rather random in its appearance even with a skilled operator. By mechanised a simple hardened template being used as a guide would do or maybe driven by a pantograph!

Pete, I have a 40 shell casing just like the one you’ve shown. The head stamp markings are “engraved” 40MM-MK3 7-45 CL-RV anchor? black ink stamped 3868

Along the side of this cartridge stamped in large black ink letters are UG-162-HA-54
Tom from MN

Howdy gents
Thanks for the input here is a better photo of the letters. You can see they are formed by a series of parallel lines of shallow dots.
But this is 1945 vintage. So Mike might have nailed it.

Still I’d like to be sure, so…

The details in this round are as follows, but I have another one or two examples using this to form the headstamp.

Headstamped ‘ 40MM MK3 3-45 CL - RV ⚓ ‘ with an electro pencil? and “3262” with a black rubber stamp, it is without a primer. A cadmium-plated steel case with black “UL-48 U-45” print and a sticker. The rotating band has a smudge so the remaining stamp is just “3-H- LOT-382”. The green bullet has a black band a red tip, spanner-flats, and the white band is stamped “MK27-1 UR LOT 3919 4 45”.

Tom it’s close to yours, & thanks very much,

edited to remove an incorrect comment

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I would rather say diamond etching because of the parallel lines.



Howdy Jo
How is diamond etching done?
And was it in use in 1945?
It was sold in my last sale but I’d still like to know about the process.

Hi Pete,

Diamon etching was an idea. I reviewed when the first industrial diamonds were produced. That was in 1953, so that is no option.
But that brings me to another idea. It is just a matter what kind of cissle is used. If this is diamond or hardened steel makes just a difference is the lifetime of the cissle but not in the general marking process.
In general you have a kind of template displaying the letters which is several times bigger than the original. By moving a pin through the template having a kind of coying gear that holds the cissle you can transfer the marking onto ever flat surface. This type of marking will not give a very deep marking. Therefore I think that it is very likely that such a syste was used. That technology was not only used for marking but als for copy lathing by using a so called curve disc where the curves represent the outside shape of the part to be lathed.



Another try, improved wording: spark erosion


Ok. How would you describe the surface which result out of spark errosion? Spark errosion causes little crater like small holes viewed under magnification which result from the micro melting caused by the sparks. What is shown in the magnified photo are lines where I assume a kind of scratching process.




What you receive from craters placed close enough is an appearance of lines. But what I see on my screen are no scratched lines but successions of craters instead. Maybe my screen’s fault.


I see your point.
I think your thinking is possible.
It would be interesting to know at what time the spark errosion was invented. Any idea?



Jo, I checked the internet before, unfortunately without success. Hans

Hi Pete,

I can help adding that the manufacturer of the case is Conlon Corp., Cicero, Illinois.



Pete, not 100% sure, but I think this might be from a “pin stamp” (aka “dot peen”) machine. It is done with a vibrating stylus (similar to a handheld engraver) that makes a series of small punch marks, but controlled by a machine. Currently these are controlled with a computer and before that a PLC (programmable logic controller) would have been used, but obviously not in 1945. In any case, regardless of the mechanics of marking, it would need to be controlled by something, so maybe an analog mechanical computer or even a pantograph with a template. But I think it is likely that the actual method of making the dots is probably mechanical based on the date of manufacture.


Thanks gentlemen.

At the time I was cataloging it, although it is out of his area of expertise, I asked Frank Hackley and he was also unaware of the name of the process.

So I think I’ll stick to Mike’s (Eightbore’s) explanation due to the time frame, although it sure would be nice to know. And Larry does allude to Mike’s thoughts.
There were, I think, either two or three of these in the listings of 40mm’s.


This is the type of machine we had but going back to the 1960’s it was not computer powered but Hydraulic/Hand powered. You loaded a template to the right hand side and it could be set at a few different scales i.e. 4:1, 5;1, 6;1 etc. By hand you then steered a stylus round the template, the speed you could do this was controlled by the machine and it reproduced the letters/words/pattern etc. on the component. I was an apprentice in those days and it was only used on “special” parts for the MOD and before I finished my apprenticeship it had gone, for love nor money I can not remember what make it was It possibly could have been specially made as we manufactured lots of “specialised” items for the MOD and their subsidiary spin-offs, FVRDE, ROF’s, ASTD, etc.

What you see here is set to quite a course finish but it shows the method very well and how quick it can be therefore cost effective when doing small batches.

Obviously you could set the machine to various speeds and feeds and depth which gave a wide coverage of indentations of size and shape. Depending on the styli you could vary the style of the indents considerably too.


Edit, was for bad grammar.

Hi Mike
So if I understand this sort of machine could have created the headstamps but you can’t say it existed in the time frame in question?
I must say in looking at the headstamp it does look as if a series of punches / dots was the method used.

And I suppose the tool could have a set of parallel “points” apply the marking?

That several lines of the M’s are a little shaky does lend credence to a hand operator.

Thanks to everyone for the input.