Please Help Me With This Spanish Stamp

I have looked in the 2017 Scot and I tried Stampworld and I can't find this exact stamp. This is another workhorse of its time I believe as there are several iterations of the set with King Afonso III facing left - some have overprints, this one does not.

The stamp color looks blue to me but I see the 15 centimos stamp listed as being slate green, my eyes are getting old I could be seeing the color wrong, but I also saw one with this design in 15 centimos which was black. I am guessing that this is Scot 409 but that seems wrong to me because of the slate green versus blue issue I have with this stamp. Here is a closeup of the stamp, sorry the quality is not as good as I would have liked:



Now that I see the stamp up close on the screen I can see tinges of green, so it seems there probably is no color issue.

What I am trying to do is date the postcard it is on. The only clue I have is the stamp on the card since I can't read the postmark so well at all. I have posted this card in the forums before, here:




I am trying to date the postcard and the only thing I have to go by is the stamp. I have a perf gauge on order, but it has not arrived yet and my older one is not available - I thought that might help with nailing down the correct stamp number.

Thank you for your help if you are so inclined. Julie

Try 1930
King Alfonso 13
15c
SG586 Scott 409 (Slate Green)
(Like those embroidered Postcards!)
Date on the Postcard seems to be August 1931
Octagonal Pmk

Hi,
My stamp colors aren't very clear either.
The minimicroscope shows black, blue and green.
I think it's Scott 409 from 1930.

Thank you both so very much, Rod222 and cupram. It amazes me how you can read those postmarks when they are rather mangled as this one is Rod, but I suppose when one has gone through as many stamps as you have (as I recall you have a fabulous worldwide collection) it gets easier with practice. And thank you so much for posting the stamp - yours is much clearer cupram. Thanks to both of you for responding to my question, I do appreciate it very much - and I am happy that I finally got a stamp id correct for a change .