When readers are requested to ask for catalogs or other printed matter, the numbers by which these are known to the reader can be used for the key—as bulletin A, bulletin B, etc.
For either direct inquiries or orders one of the most popular and satisfactory keying systems is to use a coupon, indicating the publication and month in the coupon—T W 11 printed in small type in the coupon would mean Technical World for November.
Fig. 16. Reverse of Checking Card Used for a Record of Sales
A coupon to be filled in offers the reader a convenient means of answering the ad, and this has a tendency to induce a larger number of replies. Few people will fail to use the coupon or the address given. A certain very large advertiser, who uses the coupon, states that less than one per cent of his replies are without means of identification; either the coupon is used or the name of the magazine is mentioned.
To make their checking systems as nearly perfect as possible, some advertisers write to all readers who fail to use the key, requesting them to state where the ad was seen. Some enclose a postal for the reply, others enclose a printed slip, on which the magazines used are listed, to be checked and returned.
A reasonable expense is justified to find out where replies do come from, for it is as much to the advertiser's interest to continue the use of all profitable mediums as to drop the unprofitable ones. Many of the most successful advertisers, however, consider it safe to distribute unidentified replies pro rata, basing the distribution on the number of keyed replies—that is, if 30 per cent of all keyed replies can be traced to the Technical World, that magazine will be credited with 30 per cent of all unidentified replies.
When the mail is opened all replies should be sorted by key numbers, inquiries and orders separated. Then the total number of inquiries, and number and amount of orders from each publication should be ascertained and credited.