2 rare coins

I have 2 coins; first a 1910 drei mark lubeck which I bought in a job lot for around £2 and I have now been offered £50 for - and a 1876 10 pfennig, which after looking at this site it says that if it is an H issue then it's rare. So my queston is: why is the lubeck drei mark worth so much as I can't find any info on it. Also how do I know if the 1876 is an H issue type or not.
thanks
sorry - forgot to mention I only collect British coins, that's why I know nowt about these 2, so they will be sold later

Quote: PETERT... how do I know if the 1876 is an H issue type or not.

https://en.numista.com/catalogue/pieces6078.html

  Welcome to the Forum (since you joined in November)! On that page above is shown an 1876A coin.
The 1876 is on the reverse, and the A (two of them) are on the obverse - at the very bottom, one letter either side of the tail. The Topic below has a slightly different coin, but has the marks highlighted in red ...

https://en.numista.com/forum/topic2560.html

http://www.ngccoin.com/poplookup/WorldCoinPrices.aspx?category=33129&worldcoinid=96710

http://www.ngccoin.com/poplookup/WorldCoinPrices.aspx?category=118946&worldcoinid=304397&FromSearch=true

Quote: PETERT... why is the lubeck drei mark worth so much as I can't find any info on it.

https://en.numista.com/catalogue/pieces20421.html

 The 3 Mark is silver; the 10 Pfennig is copper-nickel.
So $70 to 350 against $30 to 150 - hope all that helps!