In the Netherlands it was relatively easy to get such a device for an organization. Because there you had to pay upfront for the expected postal mail. Those also came with a counter that counted back and even weighed the envelope/letter. At least the one in the army base where I was working at the time did. Although we often bypassed that part to speed up the process. Pre-sorting on weight by hand (literally) was much faster (we had to handle all military/civilian postal needs for 4 army bases and 15 auxiliary units).
Also, you'd better not exceed the agreed upon limits, or use the wrong frank with the weight of an envelope/letter. Those 'civies' would become quite hostile if we did...forgetting who they were talking to (army, having weapons and all
). Then again, the Dutch and German postal services are/were very efficient and fast. Standard postage mail would even arrive after 1 day, although that qualified to be delivered in 3 days. Even standard postage mail sent to any country in Europe or US/Canada would arrive within a day, sometimes 2 at the intended location. Northern Africa (Tunesia, Marocco) and Turkey were quite efficient as well. Other continents or parts thereof...not so much in my experience.
Here in Paraguay (South America) international mail may arrive quite fast at the national postal services, although that is not a given. Doesn't even matter if the sender paid for high priority postage or not. Also, this doesn't mean that the mail will arrive at the intended destination any soon either. Unfortunately, the rule of 3 applies here. Don't expect any mail to arrive within 3 days. More realistic is 3 weeks or 3 months. After that...consider it lost. National mail is also problematic, bills arriving on the final day that they can be paid is quite common. Automatic payment facilities, web or otherwise, do not exist here. It is quite easy to get disconnected not of your own fault.
In all the time I have been here, I don't think I have ever seen national mail being sent without stamps. Utility bills don't even have stamps at all. So I'll assume there are no such frank systems here.