ICOADS Web information page (Tuesday, 07-Jan-2014 23:59:20 UTC):

Figure 1a. Bars show total output LMR per year (1800-1889). The grey portion of each bar indicates the number of LMRF accepted for statistics; colored portions indicate rejection types: red = ZQ (not rejected from the corrected data), yellow = platform type (PT), brown = dup status (DS), blue = 2° landmask (LZ). The PT rejections were applied only for the standard statistics, so as to limit them to ship data. The DS rejections were used to eliminate "uncertain" duplicates, and they and the LZ rejections were applied to create LMRF from LMR (i.e., LMRF consists of grey, red, and yellow).

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