As you can see just from looking, the real Gunblades are from back when Flintlock pistols were used, the Images i'v gotten have been the only two i could find on the net, not knowing their actual name, as im sure they were not called Gunblades,so i cant give much information, but i will try and find info about them as soon as posible.
There are obvious diffrences that i dont need sources for however...
The Gunblades obviously differed in Size and Style, the one above seems to be around Half (mabye a bit bigger.) the size of the FF8 Gunblade (around 3 and a half, mabye 4, foot long.) , whereas the one below seems to have a palm sized handle which sugests it is a more Dagger sized weapon compared to the seemingly shortsword sized one above.
And whereas the use for the gun section ofthe FF8 Gunblade is widely disscussed without conclusion, the Real Gunblade seems to be able to actually shoot a bullet before having to resort to the Blade, as there would be no time to mess around in battle reloading.
I would say these are more for show than use, as by this time in history most fighters were using Flintlock Rifles and for close up battles cavalry Swords and Bayonets.
Against either of these these Gunblades seem to be the underdog, probobly why its so hard to find pictures and information eh?