In 1850 the following rates for samples were established:-- Not exceeding 10 German miles 1 silver groschen 10 to 20 German miles 2 " Over 20 " 3 " and for heavier packets, half letter rate. Under the Austro-German Postal Union, established on the 6th April 1850, the ordinary rate for single letters was charged in the case of samples for each 2 loth, according to distance. In 1852 the Prussian internal rates for samples were brought into accord with those of the Union. Samples must be sent in unsealed covers and must be easily recognizable as such. The maximum weight was 16 loth, and the maximum charge was not to exceed six times letter rate. In 1853 a further privilege was conceded. When sent together with a letter, samples might be enclosed in sealed covers; but in order to enable the administration to maintain a control over the use of the privilege, the postal officials were empowered at discretion to require the sender to open such packets.[512] In 1860, when the Austro-German Postal Union was renewed, the limit of weight for samples was reduced to 1/2 pound (15 loth). Following this reduction the Prussian rates for samples were reduced in 1861: for samples weighing more than 2 loth only the rate for a double letter (according to distance) was to be charged. The reduction was not followed by any large increase in the number of sample packets. Every sample must still be accompanied by a letter, a circumstance which made the application of the sample rate heavy. With a view to the further encouragement of the traffic this requirement was removed in 1863, and the despatch of samples under band, in envelopes, little bags, or similar covers, authorized. New rates were introduced as follows: 4 pf. for each 2-1/2 loth. To prevent abuse of the privilege it was provided that no article of marketable value could be sent at the reduced rate. The packet must be marked to show that it contained a sample, and might also bear the name and address of the senders, the trade mark, and the number of samples and prices. In 1871 the rate for the Imperial Postal Service was made 1/3 sgr. for each 40 grammes with a maximum of 2 sgr. Practical difficulties arose from the great increase of traffic which followed this reduction of rate. Large packets and packets of awkward shape were posted, causing practical difficulties, especially in the sorting carriages, and it was found necessary to decline to accept samples over the counter, and to forbid the acceptance of samples in roll form. The sample rate was, moreover, complicated as compared with the letter rate. While there were but two rates for letters, there were five for samples, viz. 4, 8, 12, 16, and 20 pf. In 1875 the sample rate was simplified by the introduction of a single rate of 10 pf. for all sample packets, with a maximum limit of weight of 250 grammes.