Hello Bhann, welcome!

Here is your first image flipped and cropped to make it easier to read.

The number at the top middle is from the Scott catalogue of stamps from the USA, #418a.
I searched
ebay for 'spain 418a' and no luck, so tried 418 and got the stamp with perforations around the edges (the ordinary regular way most new stamps are made).
It is the first stamp in the Christopher Columbus set Scott #418-432 from 1930. Edfil catalogue (one made in Spain, in Spanish) #531-546.
Yours is probably MNH. That stands for Mint Never Hinged. Means it is Post Office Fresh and hasn't had any hinges attached to the back to fasten it in a stamp album. Means it is worth more than a similar stamp Lightly Hinged or Heavily Hinged or just Hinged. Or used (cancelled, postally used)
Being imperforate (imperf) means being not perforated or not having the serrated edges produced by punching holes in between the stamps on a sheet of stamps.
This means (usually) that your pair of stamps is worth more than two single stamps as an imperf pair is the proof needed to say that they are truly imperf. A single stamp imperf could have been faked by cutting off the perfs so as to get more money when sold.
So an imperf pair (or more) is the ideal way to collect imperf stamps.
I do not have a Scott catalogue nor an Edfil one. You can look in your local library and they usually (in Canada and the USA) have Scott calaogues in the reference section or to loan out. Newer ones in the reference.
To move this to a 'proper' forum, well they might, but it is easier for you to just start a thread in the Main Stamp forum, call it something like Help with Imperf Spain and people will see it much better than in here in the personal section. They can give you a price.
Be warned though that catalogue prices do not mean the prices you could sell it for. Nope. they reflect only what a dealer of good and trusted name sells it for in his shop. Perhaps. To someone that really wanted it (not everyone wants everything) and in really good condition.
Probably 25% - 50% of catalogue is what you might expect to sell it for on
ebay or somewhere online. Selling to a dealer yourself will onlt get you about 10% of catalogue as they have to sell it again and make a profit.
Oh, so Scott has an 'a' after the number for Imperf, Edfil has an 's' after the number instead. Everybody's different. It's so much fun.
How's the weather over there on the Rock by the way? I am here in Halifax in -12 weather today.