'Thetic' Oval Chainring info required

[twosheds]

Hi,
I have acquired this oval chainring, with another that I won on the bay. I can't find out much about it. I wonder if anyone on here can tell me how old it is? I am guessing it is maybe more veteran than retro. Is it of any value?

It is 46 teeth and is cast alloy.
It has made in Belgium cast in it.
It has "Thetic" and it has "PAT 449504" cast in it.
It appears to be unused, with no visible wear on the teeth.
It also has 2 stars on the outer face, as can be seen in the picture.
Thanks

 

[Midlife]

Eliptical chainrings go back donkey's years, Durham were around in the inter war period I think.

Shaun

 

[Big Block]

The V-CC's News and Views 286 has this from Hilary Stone:

Thetic chainrings were available in England from around 1937. The first versions like yours was cast from what was claimed to be Zamak. Later ones were chrome plated steel. They were made to fit Chater-Lea, Williams 3-pin and 5-pin cranks. The following illustration and text is from the 1937/8 Fonteyn catalogue.[not shown here but it was in the N&V] They can be used with derailleur and hub gears and fixed wheel. They work very nicely with a fixed wheel offering a very smooth feel. They are about 13% eccentric and are designed to smooth out the ‘dead’ spots at top and bottom dead centre.

The text of the catalogue article advises "Minute research has also been made to fix the crank in the most favourable position in relation to maximum and minimum radius. This is indicated on the Chain Wheel by two stars, across which the crank should fall."

 

[twosheds]

Thanks alot for the information.
I have now found the Fonteyn catalogue you refer to.
I'm not sure what to do with the chainring - maybe it is the basis for a pre-war project!