"Optic” has many explanations (further reading click here), but in our trade it stands for a measuring device of spirits. More specific: An optic or non-drip measure is mounted beneath an inverted spirit bottle, so that a pre-defined volume of the bottle's contents drains into the measure. It works super simple. When you want to get a measure of spirit out you push up on the switch/lever underneath which pushes up an internal sprung carriage with rubber seals on both ends. This both unseals the nozzle, allowing the liquid to flow into the glass, and seals up the connection to the bottle preventing any more liquid than what is contained in the body of the measure from flowing out. When you release the mechanism it springs back allowing the measure to refill. There is a toggle mechanism inside which prevents the measure being half open. Why call it an optic you would ask? When Gaskell and Chambers (owned by IMI Cornelius UK Ltd) introduced Optic as a brand name it has a round thick spherical glass so the barman (and the client) could see there was the right amount of liquid in the measuring device. Or: allow them to better ‘see’ the ‘enormous’ dosage.
If you search the web consequently, you will find background information on these subjects. For instance from when to when did they use a certain name, or logo or other inscription. This one is still great looking. Especially when you combine it with a bottle. Click here
From Gaskell & Chambers this is an older optic, brand name Optic Pearl.
These pourers look the same as a free-flow pourer, but they have an internal mechanism to block the tube or ball after a pre-defined and calibrated volume of liquid has passed. Great example.
Still for sale everywhere at different sizes.