I am not finding much information online so I wanted to see if anyone had any info on this.
It is my grandpa's gun that he use to carry when he delivered groceries for the family store.
Just trying to get a time frame on the gun - he was born around 1910 and it looks like the serial number is 36xx.
From the wear, it looks like it was carried a lot .

I can't help much but 6.35 is 25 ACP and Mondial manufactured two models of 25 ACP pistols in the early 1900's around WW I.  The Mondial pistols were manufactured in Spain and one model is similar to the Browning designed 25 ACP as sold by FN and Colt.  The other model like yours resembles an old Savage design and I think your model was produced in lesser quantities or at least fewer were imported to the US.

I searched google Mondial 25 ACP pistol and got a few hits.  The Mondial pistols would have been inexpensive in their day and don't hold a lot of value today.  Your Mondail would be valued as a family relic and would be interesting to keep in the family in remembrance of your Grandfather.   I suspect if the pistol was cleaned lubed and inspected it might be safe to shoot a couple of rounds of 25 ACP.   I would not shoot this pistol regularly but just be glad to have it because it belonged to someone in the family.

Thanks for the info, I tried google but didn't find too much (in particular a date for the serial number).
I was interested in seeing if by the date, it could be possible that the great-grandfather would have bought it and given to his son (my grandfather).
It could be a possibility, I guess.  The pistol was in a drawer at my mom's house for the last 30 years along with some of grandpa's things.
I am glad that she remember where it was at.  It will be cleaned and put in the safe.

Cool find.