According to the law in regards to multiples you must define exactly how you are selling your multiples, regardless of media and in some states if you are in galleries you must also include a certificate of authenticity. Also in your certificate you must clearly define exactly how you intend to sell your multiples to the T.
If you sell all X of your images and in your certificate you define the rules in which you sell.
So if you say that this edition of 8x10 will consist of 100 prints then once those 100 sold out you could no longer prints 8x10 but could sell 11x14.
If you state that this edition is of 100 regardless of size for a hand printed silver gelatin print then once those sell out you could never print another silver gelatin print of that images period.
I would suggest you read this link;
http://www.tfaoi.com/articles/andres/aa4.htm
In CA you are also required by law to disclose everything when selling multiples and photographs are classified as a multiple.
You really need to research it but to make things easier for me I include a cert and detailed explanation of how I sell and what is in included for any state or country I sell in. Also I heard that in France you are only allowed 15 or 12 I think. I remember one of the members here in the past was from France and I remember him mentioning something about the law when selling multiples. Don’t quote me on the 12 or 15 but I remember something about by law you have to limit.
However, limiting an edition does not mean the image can't be used for other purposes - like calendars, etc. You just can't use them for fine art prints.
Even it is law I would still spell it out in the certificate exactly how an images can be used after it is sold out. For example something to the effect of, once this image is sold out no more silver gelatin prints will be made. Reproduction prints however can be made at any time for books, posters, magazines, calendars, postcards, digital reproduction prints, advertising or promotional purposes. These reproductions will not be hand crafted traditional silver gelatin fiber base photographs. These reproductions will not be hand signed by the artist or numbered unless in book or poster form.
So in other words and I cant stress it enough, spell everything out and be honest.