Tempted by its style and design - after all, it's Made in Italy - I bought a Delta Vintage pen on eBay. Amber resin is very beautiful, and the two tone "fusion nib" (a steel nib with a partial gold-plated overlay) looked very smart. However:
a) the space in the barrel is very short - so it won't take any converter
the diameter of the section is just small enough that the standard short international cartridges slide right out. Looking very closely at the cross section of the cartridge, you will see that most of them taper to the nipple at the end, similar to a tapering candle. And so they slide out.
c) the F nib supplied is more like a medium, at least to my taste. I write small and fine, so I often have to find an EF nib.
corresponding with Yafa, the distributor in the US, they sent me some Monteverde small cartridges. After all, paying the postage to get Delta cartridges was out of the question and, also, I like to use shades of blue that don't come in cartridges. If you look closely, the Monteverde (and Delta) cartridges look like a telescope in profile - the part that is closest to the nipple has a slightly smaller diameter. It makes all the difference.
i also found that the Monteverde mini converter will fit in the section and the barrel, although the piston cannot extend fully. It will hold enough ink to make it useful, but if you're traveling, you may want to invest in the cartridges, just in case.
I found a Knox #5 EF nib, and replaced the fusion nib supplied with the pen. Yafa had offered to get me a Delta nib replacement, but it would have been way more expensive. This cost me - with postage - less than $12.
RESULT: A beautiful pen that writes as fine as I like, using ink that pleases me! The Knox nib performs very well.
ADVICE: It was probably more work than it was worth, but if you're addicted... need I say more?