As to lists used for trials, the more usual mistake is in the use of too small a list. Some sales managers, who have mailing lists of from 25,000 to 100,000 names, profess to try out a letter with a list of 300 to 500 names. A list of this size is not sufficient to give an actual test of the pulling power of any letter. Some of the most successful letter salesmen give it from their experience that the very smallest list from which a safe test can be made is 1,000 names. _Keying Form Letters._ It is just as necessary to _key_ form letters as to key magazine ads. The key makes it possible to trace results. The question of keying is most important when a series of letters is used--which is true in most campaigns--for it then becomes necessary to check the returns from each letter in the series. When one letter only is sent to a given list, the replies received from that list can be safely credited to the letter. There are several methods of keying form letters, among which are the following: the reader may be requested to address his reply to a certain department; he may be offered a sample or some novelty; or the letter may be written in the first person singular so that replies will naturally be addressed to the writer. The writer confesses to a preference for the last named method. The average mail order buyer likes to feel that he is receiving personal attention--that there is someone in the house to whom he can write, instead of addressing the house. A personal touch can be put into the letter signed by an individual that is impossible in a letter signed in the name of the house. [Illustration: Fig. 21. Detailed Record of Form Letters Mailed] There are those who contend that only the name of the house should be used, that the name of an individual should never be signed to a letter, and who have printed on their letter heads the phrase: "_Address all communications to the company, not to individuals._" While it is perfectly proper to use every legitimate means to keep the name of the house before the public, there is a good deal of senseless fear that the prestige of the house will be usurped by the individual. In some quarters this fear has resulted in the adoption of ridiculously extreme rules and regulations. One incident in the personal experience of the writer will serve to illustrate the point. Having occasion to request a favor from a certain manufacturer--a favor which would be granted, if at all, by the advertising manager--and knowing the advertising manager personally, he addressed the request to him, using his title in connection with the name of the firm. Somewhat surprising was the following letter, received a few days later: DEAR SIR: We have your favor of the 12th, addressed to our Mr.--------, and your request will receive the attention of the proper individual.