A sign/abbreviation for "magister"

[Hans Åberg via Unicode]

> On 30 Oct 2018, at 22:50, Ken Whistler via Unicode <unicode at unicode.org> wrote:
> 
> On 10/30/2018 2:32 PM, James Kass via Unicode wrote:
>> but we can't seem to agree on how to encode its abbreviation. 
> 
> For what it's worth, "mgr" seems to be the usual abbreviation in Polish for it.

That seems to be the contemporary usage, but the postcard is from 1917, cf. the OP. Also, the transcription in the followup post suggests that the Polish script at the time, or at least of the author, differed from the commonly taught D'Nealian cursive [1], cf. the "z". A variation of the latter has ended up as the Unicode MATHEMATICAL SCRIPT letters, which is closer to the Swedish cursive [2] for some letters.

1. https://en.wikipedia.org/wiki/D'Nealian
2. https://sv.wikipedia.org/wiki/Skrivstil