Since you do not have any dates on your great grandfather
do you have your fathers name and date he was born.
do you have your grandfathers name and date he was born.
IF so take your FATHERS year, and add on 40 years, that will give you an approximated date. Hope this helps and it may help others to check their databases. OFR if you have his name and year of birtth add 20 years on to your grandfathers year of birth and theat will give an approximater year that your grandfather was born.