Sverige 20 Ore Info Help

Hi, I'm trying to find some info on a 1921 violet Gustav V 20 ore Sverige stamp.
The only thing I've seem to come across was on the website (find your stamp's value),stating it was a rare stamp and had been sold in a past auction for 3,500. Then on (stampauctionnetwork.com) it also states about the stamp being sold for 3,500.
I just need a good website to research that doesn't seem to contradict with another. I am a true amateur and learning as I go. I'm not a collector but overwhelmed with stamps that I come across and was going to be thrown away. So I adopted them and doing what I can to be easily displayed.
Thanks, if a picture would help I can upload if needed.

There's a 20 ore violet, issued on 1/4/1921, imperf x perf 10, and on 23/1/22, perf 10. Both are worth pennies. The scarce stamp from the set is the 15 ore violet with a watermark (the stamps are normally unwatermarked). Perhaps you should upload a scan and links to the auction sales.

Hi,maybe this will help you (scroll down to 384)
https://www.northstamp.com/RETAIL/S...den1-163.htm

Please show a scan/picture. Perforations and watermark are important. 2014 Scott catalogue Sweden Sc #170 20o violet is priced at 30 cents used and has no watermark.

2014 Scott catalogue Sc #189A 20o violet is priced at $4,750 used and is watermark 181.

How to Detect a Watermark

http://www.stampsmarter.com/learnin...termark.html

Picture of a 181 wavy line watermark.

The website is https://findyourstampsvalue.com/rar...nese-stamps, and then scroll down to rare Sweden stamps and then scroll down the list. The other website is stampauctionnetwork.com, and it should be on the first page that comes up just scroll down.

You need to put the stamp face down on a black surface, dampen with lighter fuel and check for a watermark. The chances of there being ine are very low indeed.

Please don't make blanket recommendations like this to someone who may not be an experienced stamp collector and might not have the needed context. They could very well grab off-the-shelf lighter fluid that has all sorts of damaging addatives rather than Ronsonol.

Ronsonol may be fine for a one-off check, but if they are going to be watermarking stamps on a regular basis, they should invest in Clarity watermark fluid.

I just wanted to say thanks to everybody and for your input and suggestions. I really like the stamp smarter website that was recommended. I really do appreciate you all and I'm sure I will have other questions in the future.