[nvader]

The reason that I heard was that it was easy to mass-engrave a single plate:

VIIIIX

For each clock, you make 4 of these, and split each block into numbers the following way:

V IIII I X

VI III IX (mirror the IX for 11)

VII II IX

VIII IIX

This lets you mass produce watch numbers with a minimum of wasted material.

[ghostly_s]

I think most clocks and watches would have the numerals engraved directly into the face, and if they were separate pieces as on a tower clock they would be either be engraved by hand or with a pantograph, but probably not engraved at all but cut out from a sheet. In any case I don't see how your method creates any meaningful economies of scale — if anything four 'I's requires _more_ material than an 'IV.'

[pfannkuchen]

Nit: Does the plate need a fifth I?

Also 12 needs to be mirrored I think.

Otherwise lgtm.

[qprofyeh]

Brilliant if true!

[JoBrad]

Doesn’t that also work for IVIIIX?

[madcaptenor]

That’s six letters. The full set I through XII uses 26 letters (if you use IV) or 28 (if IIII), so there will be some wastage.