There are misspelling and typographical errors (wrong selection and/or rotation of typefaces) here and there in Sadajiro's 朝鮮鉱床論 (Ore deposits of Chosen (Korea)) (hereinafter referred to as his original). It can be determined by comparing it with multiple materials.

For example, in his original "Part 2 Metal Deposits" - "Chapter 1 Gold and Silver Deposits" - "43. 天王金山" (Ten'nō Gold Mine), it says "平安南道 价川郡 中西面。他二面に跨る...". (The mine is at Nakanishi(?)-men, Kaisen-gun, Heian'nandō. Also it is spanning two otehr Mens...). However, from the references in that chapter, the administrative district handbooks, Mining claims (List of mines), Topographic maps, etc., it is clear that this "two other Mens" is incorrect, and "平安南道价川郡中西面、外西面の計二面" (The mine is at Nakanishi(?)-men and Sotonishi-men of Kaisen-gun, Heian'nandō) is correct. In other words, the mine is spanning only 中西面 and 外西面. We can imagine that the cause of the error is that during the preparing to print, 外 was read as hoka and the typeface of 他 with the same reading was picked up.

However, since administrative districts change, it is insufficient to make a judgment based on only a small amount of information. It is necessary to check along the time axis to see whether the name 外西面 was changed to 外二面/他二面 or not.

For example, in the official gazette of Showa 2 (1927), 外西面 appears, but in the list of local administrative area names (linked above) in Showa 4 (1929), there is no 外西面 in 价川郡, so 外西面 may have disappeared at least once. However, it is not possible to determine whether or not the typesetting was done knowing that 外西面 did not exist. In any case, it seems that Sadajiro's original is incorrect regarding the "他二面" based on various versions of several materials. (As no handwritten manuscript remains, it is unknown whether this was a mistake in the manuscript or a typographical error.)