Classic Items With Engraver/Finisher Initials

Hello.

Would someone offer a "formula" for estimating a value of items such as the attached image? Singles and blocks. Thanks in advance.

Those are not the initials of the engraver but of the siderographer who produced the plate

C.I.R. = Clarence I. Ronsaville

value depends on. Few things.

1. Can we see the entire stamp?
2. Does it have original gum?
3. if so, has it previously been mounted?

Naturally, value depends on both supply and demand.
Compared to plate number singles/blocks, these were saved in far fewer numbers.
The demand is also substantially less.
They are clearly premium pieces compared to a standard single. If I were forced to name a value, I would research ebay for actual sales data of comparable items first.

If I were selling this on ebay, I would not worry too much about a value. I would use the auction format, have a detailed title and description and show good scans of both sides. A modest start level based on the normal single and the market will tell you what it is worth in a week. This avoids the need to determine a buy-it-now "value", which may have the lot sit through many selling cycles or be an instant bargain and leave money on the table.

5-10% more than the same stamp without the initials when you find a collector of such items.

Completely agree that supply and demand dictates the price for this. And it takes at least two interested parties on the demand side to raise the price to market level. Here is an item I saw on ebay a few days ago. Opening bid was a penny. Five bidders fought to get it; the winning bid was about 3 times catalog value ($11.25 hinged).

I don't know if there is anything special about this particular set, it just shows how an auction can be used to get the best possible value.

Another thing, your auction must be seen by the appropriate customers for it to sell at all. It needs to be posted in the right category(s) with good keywords in the title for people to search for. Likely some of the specialists of these items will have a bookmarked search for siderographer initials or margin inscription and things like that.

Good luck!