He is an expert in numismatics and is knowledgeable about Edo-period currency.
Standard kanji spelling for numismatics.
Alternate kanji spelling using 泉 for 'coin'; less common than 古銭学.
Compound of 古 (old) + 銭 (coin) + 学 (study). The alternate form 古泉学 uses 泉 (spring/fountain) as a classical term for money.