TTH Cooke IIIB Aviar(ica) 8½" F6 'X5 Copying'

[peter brooks]

I've just bought a lovely Taylor, Taylor and Hobson (Cooke) Series IIIB 8½" F6 (barrel) lens. The beauty ring says Aviar (the TTH code for these F6 varieties is Aviarica) but also 'X 5' and 'COPYING' .

The Vade Mecum says of this series

Some may be engraved "Copying" and adjusted for close-up, eg 5x on a f6/8.5in lens at No511,042, which is a beautifully coated lens marked ' Series IIIB 5x Copying'.

Lens boffins:

1) How would a lens be 'adjusted for close-up'?

2) This is obviously a process lens optimised for close distance but what does the 'X 5' mean? Five times life size? Or what?

I may not fully understand your answers but I'm intrigued to know. I have several IIIBs and other Aviars and am aware that they are a dialyte type design.

Thanks!
Peter

[Peter De Smidt]

Maybe the element spacing was adjusted? 5x likely means 5x magnification.