It was Lander, was it

[أ/ أحمد البسيونى]

Please, I read in the novel The Mask of Gold in chapter 7: It was Lander, was it. (1) Why did he use "it" with Lander? and (2) Why did he not use a negative in the tag question?
These are both good questions. The sentence is grammatically correct.

(1) “It” is the subject of the statement, so it is the subject of the tag question. There is nothing strange about it.

(2) It is true that most tag questions use a negative in the tag if the statement is positive, and a positive in the tag if the staement is negative. This is called reversed polarity. Such tag questions are used to express doubt or to ask for verification (with rising intonation) or to seek acknowledgement that the statement is true (with falling intonation).

The sentence you asked about has constant polarity. That is, both the statement and the tag are positive. Note that in most dialects of English, when there is constant polarity, the statement and tag must both be positive; they cannot be negative.

Tag questions with constant polarity such as the one you ask about usually have a slightly but not steeply rising intonation. They do not express doubt. The statement repeats or infers from what was said earlier (usually by another speaker). So in this sentence, the speaker is repeating that Lander was the one who had been stealing.