What Does 'Arc' Refer To In Philately???

I just bought a reference work on Queensland postmarks. However, I could not understand some of the information pertaining to circular datestamps, so I sent a query to one of the authors. He emailed me back: 'LEFT is the measurement of the left arc on the postmark, RIGHT the measurement of the right arc and DIA the measurement across the postmark.'

I just don't get this. Aren't circular datestamps CIRCULAR? If so how can one 'arc' be a different size from the other? Am I missing something? What does the word 'arc' actually refer to here? I simply have no idea.

Is the reference to CDS cancellations that are larger than the stamp itself? I have a great many stamps where this terminology would apply ...

I could explain to you in details the CDS but preferred this simple explanation & different types of CDS from the Internet:

Please click below links:


- CDS Definition:

http://www.thetenoclockshow.co.uk/c.../view/63/43/


- Some pics of CDS:

http://www.uspcs.org/chronicle217-F...ures1-8L.gif


Well, I couldn't understand clearly the author's reply, but, maybe he means CDS "varieties" like these (note the varieties of left & right "arc" measurements. As they don't look "pure" circulars):

http://alphabetilately.com/HIsfor/CDS.jpg


http://stampwell.com/catalog/index....productId=40


Cheers

I was thinking more along these lines ... where the CDS is bigger than the stamp, leaving multiple "arcs" on the stamp.


taken from Phil's post ... https://goscf.com/t/11866

Guessing:

An arc is a part of a circle.
Mybe he is describing measuring a CDS that has
the town as part of the circle of the CDS
as shown on this scribble
How you measure the arc is another thing
probably from tip to tip.

Looking at typical Queensland CDS's may have
you arrive at a differing interpretation.

Email the fellow back and ask him to elaborate.

Just a guess, but I believe the arcs being referred to are those that I've highlighted in this image:

with Rod and tomiseksj.

The arcs from the split circle cancel that is inside the outer circular ring of the complete cancel.

See the Melbourne cancels , pic courtesy ebay seller aussiestampz:

Well done Puzzler and Tomisek
Interesting post