The Gobierno helicopter just flew by; somebody must be lost

[Perikles]

Dein oder dein?

Good try, but optional - when writing a letter to someone, even to those with whom you would use the familiar form, personal adjectives and pronouns usually had capital letters as a sign of respect. See attachment gleaned from the internet.

I use a past tense of course because these days nobody gives a flying fuck about such niceties.

[attachimg=1]

[Myrtle Hogan-Lance]

I don't believe they did while I was learning German. 

No, having just checked my remaining textbook, they did not.  It is from around the time Gutenberg invented the printing press. 

[Nova]

Is @Myrtle Hogan-Lance really arguing with @Perikles about German??   

[Perikles]

I don't believe they did while I was learning German. 

No, having just checked my remaining textbook, they did not.  It is from around the time Gutenberg invented the printing press.

You would not expect that in a textbook, unless it is an actual written letter. If there are sentences which are just dialogue, there would be no capitals. Here is an extract from a loveletter to Hölderlin, written about 1800:

Ich muß Dir schreiben Lieber! Mein Herz hält das Schweigen gegen Dich länger nicht aus, nur noch einmal laß meine Empfindung sprechen vor Dir, dann will ich, wenn Du es besser findest, gerne, gerne, still sein.

Wie ist nun, seit Du fort bist, um und in mir alles so öde und leer, es ist als hätte mein Leben alle Bedeutung verloren, nur im Schmerz fühl ich es noch.

although the orthography might have been changed. Attached is another original letter which looks about 200 years old, in which the capital letters are clearly visible in lines 1,5, 6 and 7.

[attachimg=1]

[Myrtle Hogan-Lance]

Thank you @Penkles.  I found I had another old textbook as well as my dictionary, none of which address letter writing.  I guess that is no bad thing, given I have managed to avoid writing a letter in German in the intervening time.  Should the occasion occur, I will be straight on to you.

[Perikles]

...I have managed to avoid writing a letter in German in the intervening time.  Should the occasion occur, I will be straight on to you.

By all means. The probability of your needing to write in German, using the familiar form (which they use with restraint), must be around zero. But I live in hope. 

[Janet]

big yellow helicopter circling almost directly over us and now flying back and forth ...

[Malteser Monkey]

big yellow helicopter circling almost directly over us and now flying back and forth ...

Put your pechugas away and come inside - leave them be

[Janet]

you must be confusing me with some other administrator ...

[Myrtle Hogan-Lance]

Time to do a head count on the Germans again.