I think it's from Cantonese(粵語).

珠宝店is for those stores mainly selling jewelry,and 金行is more for mainly selling gold bars or silver bars or sort of stuffs for people who want to do investment, but in many cantonese speaking areas those stores would combine them together ,like “珠宝金行”.

珠宝店 and 金行are both old fashion saying in the perspestive of late 20s native Mandarin speakers. They came up these names because conventionally, Chinese like pearl, 珠, gems/ jade 宝 and gold 金jewlery 饰品. "行 hang2" is the shop "店" where sells various of merchandize of one specific classification. E.g 金行 will be mostly selling gold related jewleries. Nowadays, Chinese speakers would prefer to say ”饰品店 shi4 pin3 dian4" and they prefer sliver jewleries now which is " 银饰店 yin2 shi4 dian4. Hope this helps. Good luck Sarah

Actually I don't think its old-fashioned, we still use it to call those jewelry stores, but few jewelry stores would name themselves like“...珠宝店”，more common is to name a name without 珠宝店， like 周生生，周大福，or六福珠宝，e t c.

In the old days, 珠宝店 sells jewelry, while 金行 = goldsmith shop. However it is more profitable to sell stones to be mounted on previous metals, the businesses merged together and sell anything that is previous. So nowadays, they mean the same. 饰品店 = accessory shop deals mainly in costume jewelry, so it is not considered a place of exclusivity.