it happened on the way to the forum: command economy or endangered specie

After the comic-tragedy of of a succession of rulers elevated, blindsiding both the nominees—ambitious or inuring and the state with no forward-looking policies in place and only filling the power-vacuum by whatever pretender might be sucked in next with the sufficient gravitas to plug the hole for a few years and sometimes just for a few weeks, Diocletian from Illyria (modern-day Dalmatia in Croatia) came on the scene, having risen through the military ranks to command the cavalry during campaigns in Persia and on the Danube frontier and radically reformed the way the Empire was governed, by turning the state back to the role of state-craft.
In order to prevent any potential usurpers from raising a fighting force that could unseat the incumbent, during the reign of Aulerian, the Emperor had taken personal charge of the bulwark of the legions and when crises emerged, marched his private army to whatever new insurgency, domestic uprising or incursions on the borderlands, was presenting itself. The tacit seemed to bring a measure of stability to the Empire, with Aulerian's tenure exceptionally long and productive compared to other office-holders of the time, but was very taxing and inefficient, given how the troops had to rush to counter any and all threats, and threatened to endanger the Empire any time there was an attack on more than one front. Realising these risks, either sacrificing border-security for the safety of the regime or vice versa, Diocletian took the bold and ingenious move of sharing imperium—first with a trusted co-regent—and then splitting the Empire into four united regions, reasoning that no man could let his ambitions get the better of him ruling a quarter of the civilised world with virtually full autonomy. Tax havens were eliminated and no province, even what had formerly been the home province of Italy, was accorded especial treatment, with capitals established at Antioch (on the Syrian/Turkish border), Nicomedia (near the more famous Constantinople), Milan and Trier, and demarcating a division of skill-sets that was not distinguished before, created separate military and civil-service career tracks that put professional administrators in charge of tax-collecting, the courts, assessment and public-works projects.
The bureaucratic hierarchy established put the persons of the Emperors behind endless corridors of intermediaries, answerable to the next higher officer, and lent them an air of almost a demi-god and not the the aura of the First Citizen, a common-man brought up in the ranks of soldiering and fraternising with the people, putting forth the principal of rule by the grace of God, the divine right of kings. The Empire consisted of around one hundred small provinces, which were grouped into larger political units called diocese (of the same Greek root for administration as the cognomen Diocletian), under the governance of an ombudsman called a vicar. These vicars coordinated the larger federal policies among the regional powers, and this structure was preserved, with essentially the same borders, by the Catholic Church after the Fall in the West to the present day. Of course, this apparatus was not just put in place to shield the upper echelons of leadership or to protect personal and dynastic interests, but rather, there was a lot of business, civil-affairs and economic-recovery, to attend to. These matters had been neglected for years, with emperors expected to preside over decisions large and small in trials and policy and near continual debasement of coins, reducing the precious metal (specie) content which resulted in inflation. Diocletian knew that simply coining more money made it worthless and began to round the worthless coppers and slugs and minted new currency of nearly pure silver and gold content.  His attempt was a worthy one, but Diocletian and his ministers did not take nearly enough of the old coins out of circulation and his successors did not enforce all the elements of the recovery plan, as tradesmen and later governments did not understand the economic principles in play. Money was still not worth its face-value.

Because tax revenues were falling precipitously and pur- chasing- power was declining, Diocletian suggested another bold reform that simply removed the intermediary of money and instituted payment in-kind. Sending out his legion of bureaucrats to take stock of what non-liquid assets every one possessed and how much each family needed to live, they returned and constructed a comprehensive equivalency chart to, without the medium of money, show that so many hours of work in the fields or of tending the herds or of soldiering or of shuttling munitions or of arrow-making, etc. was equal to so many units of grains, bolts of fabric, jugs of wine, tableware, etc. This thoroughly researched commissariat determined the annual budget for all the land, and actually functioned pretty well, leading to a better and more equitable return of services in exchange for what the Empire doled out. Barter such as this was naturally not conducive to international trade, the rest of the world having been introduced and now hopelessly accustomed to the Roman coin, but helped to stabilise the economy and replenish state coffers with fiat money. Diocletian even anticipated what might happen if everyone went after the easy or glamourous jobs, like prospector or astrologer, instead of more menial and harder work in exchange for their stipends, like garbage-collector or butcher, and called for the formation of trade guilds which set quotas and applied standards for admissions. Though ultimately the Empire fell in the West over invasion, military coup and economic implosion, Rome did go on existing for another one hundred or so years, already moribund when Diocletian came to power, and chose co-regents that allowed the Empire in the East to survive for another millennium. Diocletian retired graciously, the first and only Emperor to abdicate, to his homeland.