Decoding Hermagis lens writing!

[Steven Tribe]

There is a long running thread on Hermagis serial numbers and dating on the brass and lens edges. Apart from the last two digits of the year in the 19th and 20th centuries, there are usually a meriad of digits which have no obvious interpretation!

Rather than clutter up the thread on serial numbers I (we) thought it might be useful to have a separate thread on these elusive digits and their (possible) meaning. This is a very minority interest compared with serial numbers/dates of Hermagis but it would be nice to solve some of the problems.

It looks like the numbering system changed during the production period as well as the total of numbers given. What is certain is, that it not just a simple registration of exact focal lengths, the specific model or a matching system of individual lens components.

Some of the following are possible, I think:

- an internal stock/batch production system - perhaps even relating to the glass block the lens was cut from.

- a staff identification number. We know from the Dallmeyer archive that records could be kept of both turners and finishers. The pencil names of workers do appear on other lenses. I have some support for this as I have two lenses from very different Petzval sizes that both have 209 written on them.

[Amedeus]

... I have two lenses from very different Petzval sizes that both have 209 written on them.

If memory serves me right, then one of the achromats with 209 on them had indeed a focal length of 209mm ... what is the focal length of the other one ?.

There's a myriad of possibilities ;-)

Cheers,

[lucaas]

Hi Steven,

The lenses I posted in the serial number thread have different numbering pattern.

For portrait no.6 57620,
on front cell: (513 - 514 + 17)
on one rear cell: (518 - 563 + 17)
This looks like stock number or production batch number.

For extra rapid no.4 65758, it has letters

This looks like the worker's name.

For eidoscope no.2 41650, it has something that I can't recognize