North German Confederation Wrapper, Need Some Help With Postmarks Please!

Can anyone supply any info on the rather tatty wrapper I picked up recently? It was posted in Bochum, Germany and carries an 1870 official stamp of the North German Confederation. It appears to be an invoice for something. The front carries two rectangular marks for Bochum, and 1 3 12 1. So first question is what do the numbers relate to as they cannot be the date? The reverse carries a blue mark with what looks like a crowned eagle, and 'REICH' & 'BOCHUM' and one other word in a circle. Also a circular mark with 'AUSG' over '2' but the rest is missing. Can anyone identify these marks? Thanks in advance.
Best regards
DavidR

The 'Ausg.' marking, if memory serves, stands for 'Ausgabe,' which indicates an attempt at finding the addressee.

It is the date, March 1. Year is not indicated. 12 - 1 is the hour. There may be a year shown on the invoice but I can't decipher it. The stamp is an official stamp.

Thanks for your help gents.
Regards
DavidR