The large increase of traffic which resulted made desirable a simplification of the definition of packets entitled to the privilege. Only communications of general application could pass, and the officials found themselves often in doubt as to the application of the existing definition. Thus, notices of the despatch of goods, invitations, or printed letters could not be sent at the privileged rate, while, e.g., notices of marriages could. So far as the Union was concerned, in 1860 the privilege was limited to documents reproduced by mechanical means.[483] The maximum limit of weight was reduced from 16 loth to 1/2 pfund (15 loth). This definition was introduced in the Prussian inland service in 1861. The rate of postage was also modified in that year. The rate of 4 pf. for each loth was retained, but with the proviso that the charge on packets sent under band should not exceed twice letter rate. This effected a great reduction of charge for the heavier packets. Whereas previously the rate for a packet under band weighing 10 loth, sent more than 10 German miles, had been 18 sgr., it now became 6 sgr.[484] In 1865 a special rate of 4 pf. for printed matter sent in the form of an open card was introduced in Prussia.[485] The simplification of definition and reduction of rate resulted in a large increase of traffic. In 1867, when the North German Postal Services were unified, the penalty for abuse of the privilege was reduced to a surcharge of four times letter rate, but not less than a thaler; and the law of 1871, founding the Imperial Post Office, abolished the fine because it had been found that the offences were for the most part committed through ignorance of the regulations. Slight changes were made in the regulations under which printed matter was admitted to the privilege, but no change was made in the rates of charge. The law regarding the Imperial Post Office (28th October 1871) left the fixing of rates for printed matter to the Imperial Chancellor. The maximum limit of weight was raised from 1/2 pound (250 grammes) to 1 pound (500 grammes). The rates of postage were 1/3 sgr. for each 40 grammes up to 250 grammes, with a maximum of 2 sgr.; from 250 to 500 grammes, 3 sgr.[486] The large increase of traffic resulting from the reductions in the rates for printed matter and for samples caused practical difficulties, and in 1873[487] the acceptance of letters, postcards, printed matter, and samples was to be only in the _Briefkasten_. In 1874[488] the limit of weight for printed matter was raised to 1 kilogramme, and the rate was made-- Not exceeding 50 grammes 3 pf. 50 to 250 grammes 10 pf. 250 to 500 " 20 pf. Over 500 " 30 pf. In 1879 (order of 8th March) the definition of printed matter was further extended.[489]