Simple answer is that money changers were used during the high/late middle ages & early modern times. Coins were backed by their metallic content, not governments, so money changers had lots if different types of scales & books on conversions. Many are extant today.

Only royalty had bags of gold. They had people who handled that sort of thing for them, and they had plenty of guards. Often, large quantities of gold and silver received from another state or country was melted & reminted in local coinage. Theft of such quantities was not practical, as there was no easy way to transport the loot -- gold is heavy, and a few hundred thousand goldgulden couldn't be carried off on a couple horses.

Coins widely circulated outside their native states & countries, unlike today. That's why neighboring states & countries copied each other's coin types, particularly when one was a regional standard.

Most lower classes didn't have enough coinage to bother robbing. They often had no coinage outside of once or twice a year when they sold crops. And those that might rob them needed to be more careful -- it was a lot simpler for officials to sentence hanging or mutilation, and getting murdered by your victim's brother was not as high risk as today.

Early banks in the late middle ages often lent money to royalty, usually at high interest rates (way higher than modern times), but it was more to fund wars & personal royalty stuff like feasts & cloth than from getting robbed.

(http://www.autoadmit.com/thread.php?thread_id=5550264&forum_id=2Reputation#47813320)

(http://www.autoadmit.com/thread.php?thread_id=5550264&forum_id=2Reputation#47808495)

A popular theme of the literature of the time were rogues, either gentlemen who betrayed the code of gentlemen, or fakes pretending to be gentlemen. That tells you how serious the world of the time took the concept of gentlemen.

(http://www.autoadmit.com/thread.php?thread_id=5550264&forum_id=2Reputation#47808517)

you don't say!

(http://www.autoadmit.com/thread.php?thread_id=5550264&forum_id=2Reputation#47809010)

The ill-concealed tensions between the expedition and coastal Indians was the legacy of experiences and misunderstandings on the journey down the Columbia. After the nasty encounter with the Skilloots, the explorers began to build a negative image of river and coastal peoples that colored relations throughout the winter. That powerful image was a composite of several related attitudes about Pacific Northwest people and their lifeways. A principal element was the perception of Chinookan peoples as incorrigible thieves. The theft of expedition goods and the fear of losing weapons was behind much of the provocative language directed at the Indians. Clark would have found substantial agreement in his ranks when he branded the Chinookans as "thievishly inclined." [29]

But it was more than a belief in their criminality that led the explorers to view their Indian neighbors with suspicion and sometimes open hostility. During the days at Point Ellice and Chinook Point, the expedition often depended on nearby Indians for food. The Chinooks and Clatsops, accustomed to hard bargaining with whites in the sea otter trade, expected to drive equally hard bargains with the hungry explorers. Lewis and Clark clearly resented paying "immoderate prices" for essential foodstuffs. When some Kathlamets came offering roots, skins, and woven mats, "they asked such high prices that we were unable to purchase anything of them." [30] What Indians saw as simply good business and the Yankee law of supply and demand looked quite different to hungry and wet Americans. The Chinookans, so it appeared to Lewis and Clark, were not only thieves but sharp traders bent on gouging the needy. There was no trace of admiration in Lewis's voice when he declared that the Clatsops were "great higlers in trade and if they conceive you anxious to purchase [they] will be a whole day bargaining for a handfull of roots." It did not take many days of fruitless trading for green fish and roots in a pouring rain to convince the explorers that coastal Indians were possessed of an "avarcious all grasping disposition." [31]

To the image of thievish and grasping Indians Lewis and Clark added a third element. They found many Chinookan customs and practices both incomprehensible and reprehensible. Although the expedition always viewed Indian life through the filter of its own Euro-American values, there were native ways, especially on the northern plains, that the explorers found praiseworthy. No such praise was offered to coastal peoples. Lewis and Clark repeatedly described the Chinookans as dirty, poorly clad people who engaged in such barbarous customs as head flattening and ankle binding. Coastal sexual practices also came in for much pointed comment. During the Fort Mandan winter, sexual relations between village women and men in the expedition had been commonplace. Although concerned about the spread of veneral complaints in the ranks, the captains had been muted in their criticism of those Indian women. There was no such reluctance to vilify the coastal women. From the time of the first sexual encounters with Chinook women in November, Lewis and Clark blasted them as promiscuous sellers of their own bodies for trinkets and bits of ribbon. [32]

Finally, and perhaps most important, there was the matter of the physical appearance of coastal Indians. Every culture promotes its own image of an attractive body. The Indians of the northern plains came quite close to the somatic norm held by the explorers. But the Indians Lewis and Clark found on the lower Columbia and on the coast did not fit the Euro-American image. Shorter in stature and possessing facial features quite unlike those of the plains natives, the Chinookans appeared to the explorers as "low and ill-shaped." The fact that these Indians were superb canoe navigators, masterful traders, and skillful fishermen was often overlooked as the expedition stressed what it saw as the negative aspects of a "badly clad and illy made" people. [33]

In many ways, reaching the Great Western Sea was an anticlimax. Certainly all members of the expedition were exhilarated by the sight of the ocean. There was a sense of achievement in knowing that they had passed the tests of a hazardous land. Clark's own enthusiasm emerged when, taking a cue from Alexander Mackenzie, he carved on a big pine tree: "William Clark December 3rd 1805. By land from the U. States in 1804 & 1805." As Clark recalled, his men appeared" much Satisfied with their trip beholding with estonishment the high waves dashing against the rocks & this emence Ocian." [34] But those feelings of excitement and accomplishment were tempered by relations with new neighbors that were already less than cordial. Throughout November, as the explorers suffered in the rain and cold, they were increasingly willing to use threats against the Chinookans. Given their experiences with other river bands and the constant problem of theft, Lewis and Clark surely felt justified in telling the Indians that they would be summarily shot if caught stealing guns or other weapons. Short on provisions and confronted by native traders who demanded high prices for their goods, the explorers felt trapped. Resorting to threats satisfied their desire to be in control of a difficult situation, but it spread fear and suspicion among the very people the Americans needed as winter allies and friends. Hemmed in by an inhospitable climate, an uncertain and monotonous food supply, and a language foreign to all expedition ears, Lewis and Clark faced a winter whose hazards were no less real than they had been at Fort Mandan. Whether their Indian neighbors would exacerbate those dangers was still unknown.

(http://www.autoadmit.com/thread.php?thread_id=5550264&forum_id=2Reputation#47808760)

There was paper money pretty far back, but it was equally subject to theft and would be taken at a discount if far from home. If you are some English guy passing through with a piece of paper that says "turn this in for 50 pounds in London", it is not a trivial exercise for the recipient to redeem that note at full value, and if it turns out that you wrote it yourself, you will be long gone before he figures that out.

(http://www.autoadmit.com/thread.php?thread_id=5550264&forum_id=2Reputation#47810702)

Silver coins were standard, but not always common -- the smaller denominations, often of token value, were the workhorse of monetary trade; especially so during recurring bullion famines.

(http://www.autoadmit.com/thread.php?thread_id=5550264&forum_id=2Reputation#47813263)