50 Pesos El Banco Nacional De Mexico (1913, & s260)

From my smaill knowledge base it looks to be worth a little over US $100- but it depends on the condition and if it has adheared to the plastic sleeve it appears to be in.
We have others on the forum who are experts and I would wait for their reply.
by the way

Welcome to the forum

Really nice note. Appears to be "VF" to "EF" (Very Fine to Extra Fine) from the single picture of the front you provide. It you wish to get a more accurate opinion on its condition, you would need to post another picture of the back (reverse).

I have very little experience with Mexican banknotes but I have found one like yours on the BM (Banknote Museum) site. Yours appears to be P-260d & since its "series BE & SE" (red letters on bottom left & top right), I'm assuming it was a later issue than the one pictured on this site:
http://www.banknote.ws/COLLECTION/c...MEXS0260.htm

I highly doubt ebay will be any help to get an approximate value of your 1913 50 Pesos note. I feel your best bet is to check out Heritage Auctions (past sales) or just take the note into your LCS (Local Coin Shop) & ask a dealer. Buy some currency sleeves & perhaps sell some of the other more common notes & he/she will be even more helpful. [You can probably double the estimate the dealer gives you & once you buy some sleeves or supplies you may notice his estimate increase ] The thing is- he/she has rent to pay so they have to make a profit & it will cost you to sell your note (keep that in mind).

Here's Heritage Auction's site:
https://currency.ha.com/rare-world-...world-061722

And here's my NC SITES & FORUMS page which has many online World sites that may help for further reference/opinions on your inherited collection:
https://sites.google.com/view/notap...sites-forums

Finally, good luck in discovering what you have inherited! Please keep us updated