Franklin - Scott Nr. 300, With Two Guidelines ?

I recently obtained a Scott 300 with two guidelines. One horizontal at the top, and one vertical on the right side of the stamp. Since I have never owned one before and actually never seen one, I am wondering if this variation is found often or somewhat of a rarity?
I have been looking through the Scott Specialized Catalogue but have not been able to locate a listing for this stamp. Lastly, since I have not found a listing of the stamp, I am curious as to the value of such a stamp. Perhaps someone can help me out with this. As always. I thank you very much for your help,
Pete

If you look at about page 24A-25A in the introductory section of your specialized, you will find a diagram like below. Your stamp was printed in sheets of 400 then cut along the central guidelines into four panes of 100 for retail sale. Your stamp comes from the orange-shaded square, the upper right stamp of the lower left pane. The lines and straight edges are natural parts of the production process. They have no special catalog listing status. Value is minimal.

Hallo John Becker,
Thank you very much for your quick reply and help. Tells me that I still have a lot to learn.
Thanks again, Pete

On the bright side, the two guideline stamps are technically uncommon for the sheet (only 4 in the 100 sheet stamp). Not more valuable than the others in the sheet, but it might make for an interesting type of set to collect!

To build on fini32's reply, here are the four corners as they came together at the center of the press sheet of 400, showing the guide lines along the straight edges:


Many decades ago, some collectors assembled mini-blocks showing the guide lines all around the perimeter of 9 stamps, although eye-appealing, this is not accurate to the way they were originally printed:


In general, demand for these straight edge stamps has waned.

Here are 3 scans from a circa 1935 price list booklet from a dealer in such guide line stamps. Note Scott 300 is within the group at the lower left of the last scan. The #300 corners are priced at 10 and 15 cents each! Not inaccurate to current prices.






As a disclaimer, lines on flat, offset and rotary stamps (and sheets, booklets, and coils) can mean completely different things, have different reasons for their appearance and have substantially different values. Not all lines are created equally.

Is there a list somewhere that shows all Scott numbers that were made on 400 pane sheet (that contain a cross centerline block?