Already being a cursive font, the addition of the three non-three's is like a bit of comedic effect, thrown in by the designer for amusement. I am sure it had a purpose, but it will confuse just about anyone not versed in the meanings of the slight variations.
The aa with a bar is driving me crazy. I searched and searched and couldn't find any info on it.
Oh, actually, I finally found it. It stands for the Latin ana, which means 'of each'.
Really? The only definition for ana that I can find in online Latin dictionaries is "aged" (feminine form). If it means "of each" (which would seem appropriate in some prescriptions) then it's roughly akin to @, meaning "at the per-unit price of X." In some parallel universe, people are using Michael's double-a character in their e-mail addresses instead of the obscure @.
OK, you're right. It seems to be medieval Latin, taken from the Greek:an·a (ăn′ə) adv. Both in the same quantity; of each. Used to refer to ingredients in prescriptions.[Middle English, from Medieval Latin, from Greek, at the rate of; see an- in Indo-European roots.]ana (ˈeɪnə; ˈɑːnə), adv. 1. (Pharmacology) pharmacol (of ingredients in a prescription) in equal quantities. Abbreviation: aa [C16: via Medieval Latin from Greek: of every one similarly]Source
Right, seems to make sense. And here's a list of abbreviations I found from an old nursing textbook. http://i.imgur.com/QdTcP7S.png
I kept forgetting to add that _a to my previous blog on the apothecary typewriter. (here repressed _aa). I personally think we're probably looking at a machine that was owned by a pharmacology student. Probably a young woman. Interestingly, the apothecary measures were largely considered obsolete by the 60's and by 1965 these measures were almost completely removed from use. To that end, I'd suggest that the SM7 in question probably dates to quite early in the model's run. I'd hazard a guess that this machine was a gift to a student by their parents, who had the characters changed specifically for their daughter - who probably showed a love of the script typeface.
My readers are brilliant.
That said, the ℞ symbol os conspicuously absent. Although the upper case M does seem to conveniently cover the missing ♏ 'minim' measurement.
The handwriting of medical practitioners in notoriously illegible, so I think the cursive script is a deliberate step in that direction..