A big question. The U.S. money order system goes back to 1864:
(Marshall Cushing. "The Story of Our Post Office" 1893, pages 202-225, a very useful book on postal operations.)
I know of no specific detailed source for the full story, but if I were researching for basic primary source information on the money order system, I would be looking through the "Postal Laws and Regulations" volumes and the "Postal Guides". They would give a decent picture of what documents may still exist today.
Over this time span, there are numerous versions of the money order document itself (the early ones quite pricey), the application forms, the internal accounting documents, the postal markings, official mail envelopes, etc.
The USPOD Official Postal Guide does show some models of Money Order Forms such as Page 26 of the July 1914. Generally the July issue is the annual issue and the other months are supplements to the annual and to the then current Postal Laws and Regulations (PL&R) which for 1914 is the 1913 PL&R. When supplements were not issued monthly this changes somewhat with at least one the "annual" and the balance supplements. After a certain point, the guide was split into part one (domestic mail) and part two (international mail).
As an aside, the monthlies listed money orders reported stolen using the serial number(s).
Stampsmarter.org has PDF images of the Postal Guides, annual and monthly. You can find the image I mentioned above there. Go to the home page, click Library, click USPOD Publications, click Postal Guides 1908-1920, click 1914 Annual.
PPG, I mean both the USPS and its coercive monopoly predecessors going back to the beginning of money orders. Heck, if Lysander Spooner issued money orders, that would be interesting too.
I had found a big document from the 1980s, but I can't find it today. I need to organize better. It might have been a USPS OIG analysis, or maybe Congressional, and it went into design changes and upping the max money order amount to $500, then $700. (I think it's $1,000 now.)
The USPS OIG reports are very interesting in general. They expose a lot of mismanagement, waste, and likely thefts that they don't seem to be able to do anything about. It's a treasure trove for management, organizational behavior, and monopoly culture researchers. They also evaluate service levels, and sometimes propose business innovations like expanding the money order business into e-payment products.
That StampSmarter website is one of the most amazing websites I've ever seen...
Quote: both the USPS and its coercive monopoly predecessors
Kinda makes me step back and ask ... Where are you trying to go with this topic??
Regardless, just like U.S. and foreign currency, the U.S. money orders have slowly incorporated security features to make forgery and alteration more difficult.
Theft: True in nearly every organization. It may be a case of how much time/resources can the USPS spend chasing a $100 or $500 theft? Walmart builds this into their overhead. Also, is the rate of money order fraud/theft any worse than your local bank down the street, which won't tell you their losses?
The USPOD and the USPS did not and do not hold a monopoly on the issuance of domestic money orders. For example, many express companies issued money orders for their customers.
To be clear, the monopoly was just for first class matter. Any downside of the monopoly, in my opinion, was balanced by the support it gave to the expansion of the railroads, roadways and airlines which carried first class and other classes of mail.
Study the start of the 1913 Parcel Post System and you will see it was to break the monopolies of many express companies for the good of citizens and business alike.
John, by theft I wasn't referring to money orders. Those OIG reports were about a station or annex missing tens of thousands of dollars in stamp inventory, and in some cases cash. I don't think I've read of any cases of USPS employee theft of money orders, though statistically it must happen. The only money order thefts I've read about were by burglars breaking into post offices, sometimes stealing the machines as well. There was also that famous money order scam run out of a US prison around 1990 ± a couple of years, where inmates were doctoring money orders (postal, I think) to increase their amounts, then getting people to cash them on their behalf or something. It was a huge operation.
My interest in postal money order history isn't focused on security or forgery issues – it's a general interest, and I like the design history of important documents, stamps, banknotes, financial instruments, ephemera, etc.
As far as comparative organizational issues, any monopoly, especially a coercive/government monopoly, is going to foster a different culture and behavior in countless ways. This is understudied, probably because of political bias (I'm principally a social psychologist, who sometimes publishes research on political bias in the field and how it undermines research), but we know about the complacency and lethargy effects of monopolies and government agencies, especially where there is extreme or extraordinary job security. There's nothing inherent about government as such that would necessitate extraordinary job security for its staff, but it just tends to go together for whatever reason. This feature will act as a selection filter for the kinds of people who will tend to pursue employment there, and it will shape behaviors and the culture for those who are hired. All large organizations struggle with spending and waste issues as well, partly due to the incentive problems in that the money is never an employee's own money, but government agencies will perform worse on average.
USPS staff have striking dispositions and assumptions compared to say FedEx or UPS staff. We'll likely never see that kind of extreme complacency and entitlement in a private carrier for more than the couple of years it would take for it to go out of business as a result. But even that's hard to imagine, since the factors that would cause such a culture to sprout simply don't exist in a non-monopoly private-sector carrier context. For example, the USPS is the only paid service, business-like organization that I know of with an 800 number where it is literally impossible to reach a person – 1-800-ASK-USPS leaves you stranded at every branch of their phone tree. I've never seen that except with government agencies. I know of cases where USPS staff literally don't even respond to questions, say by a confused business shipper doing a drop-off of packages out back. That shocking non-response behavior is something I've only seen in coercive monopoly contexts like the NYC taxi driver who fully ignored us – we were in his taxi, and every question we asked he simply wouldn't respond to or speak, intentionally ignoring us. It wasn't a language or hearing issue – he decided he wasn't going to speak to us, and didn't care that we were paying him. Bad day? Maybe, but it will never happen with an Uber driver. Pretty much every variable is going to be worse than private-sector carriers, except package shipping costs, which leverages the letter mail monopoly. I like stamps, but not monopolies.
Hope this helps with you study. Yes, many studies go beyond the postal aspects of the topics. Unfortunately, some collectors do not appreciate that the postal element is just one part of a bigger picture. Enjoy your hobby and quest.