Muhammad bin Tughluq's token currency experiment attempted to assign silver-tanka value to coins made mainly of what?

Copper and brass is the defensible answer to this advanced Medieval History question. Muhammad bin Tughluq issued copper and brass tokens at a value comparable to the silver tanka, but uncontrolled counterfeiting undermined the scheme. This problem belongs to the institutional history of the Delhi Sultanate, where authority depended on mobile military elites, revenue assignments and close supervision from the capital. Administrative terms must be distinguished carefully because a department, an officer and a fiscal assignment performed different functions. The distractors need separate rejection: Gold belongs to a different institution, context or chronology; Lead does not perform the function described in the stem; and Iron fails the required association. The wording of “Muhammad bin Tughluq's token currency experiment attempted to assign silver-tanka value to coins made mainly of what?” is deliberately specific, so the candidate should isolate its operative clue before recalling names. A useful method is to construct a two-step link from the tested term to its function and then from that function to the relevant ruler, text, monument or region. The fact is significant beyond one MCQ because it reveals how medieval institutions worked in practice and how historians classify the surviving evidence. — Copper and brass”, but also remember the factual reason stated above.