I'm not sure I can help with the tail of lower case letters not showing up.  But when I had a couple of letters, such as a and e, with the space inside filled with ink, like in your example, I was able to fix that by indivudually cleaning each letter on each slug.

I used Naphtha, lots of wooden toothpicks and lots of Q tips to clean out the hardened ink in and around those tiny spaces.  It made a world of difference, and now the type is so crisp and clean, and all the letters on the slugs look shiny and new.

Hi Zac, I can tell you straight away that your type needs cleaning. it's unlikely that on a 90-year-old machine you'll get pristinwe and perfectly aligned type, so your ascenders or descenders might still not show up. But your issue is letter by letter: the ascender on the t shows up fine, as do the h and your capitals. So your best bet is to clean everything up and see what you've got then. If you have an Olympia, they come with a really nice wire brush for cleaning the type. It does sound as if you're going to need the toothpick option, too, but don't use anything metal in there that could scratch your letters. 

I'd also recommend getting sdome platen cleaner, or rejuvenator - Uwe put me onto that and it can make a real difference. And always use a backing sheet, to protect your type faces, especially if you have a hard platen! Think what it does to those little raised letters, bashing into a hard surface over and over. 

Ahn, I don't know about brake fluid... Maybe Uwe will see this and comment - I'm in the UK and all the brands and even words for things are different, but the stuff I got off amazon or somewhere is called 'Automation Facilities AF 100 ml Platenclene Cleaning Pump Spray'.

Uwe wrote:

A search of the forum for rubber rejuvinator will turn up all the threads that discuss the various products available. As for brake fluid, I wouldn't put it anywhere near a typewriter. The stuff eats paints and a surprising number of other things too - very effectively at that - and one small mistake can be costly. I also don't see the need for using such a harsh chemical when there are products on the market specifically designed for the job. I have seen professional typewriter repairmen use brake pad cleaner on typewriters, but that's an entirely different product and was used for an entirely different purpose.

Okay.  I will keep that in mind.  I guess unsound advice can show up anywhere.

That type sample still looks awfully messy. The quality of the imprint is much improved, but it almost looks like the ribbon is dragging across the paper, which normally only happens if it isn't spooled through the vibrator correctly. Then again, it's also possible that you're using a lighter weight paper and you have type on the other side of the page. How did your OCR test work out?