Labels / Stamps On Back? Belgium? Identification, Or Any Ideas. Please .

Near sender address nr. 40, Fort 5 Street in Elsdonk / Edegem.

Is your friends' initials "AI"?

I have my doubts about savings stamps with a face value of 19 (centimes). Those face values would, almost certainly, be in multiples of 5 or lower than 5.
These would have been stuck in a savings stamp booklet. The date is very doubtful on a savings stamp. An end-of-validity date for savings stamps is daylight robbery. A start date is simply nonsensical - of course, it is Belgium - as you would not issue them before such a date. Also the ornate use of such stamps seems extremely wasteful, especially for 1946.

Just FYI, I have no idea about the comments about AI - my friend, whom I trust implicitly, has this cover in his possession. Can somebody explain? Thanks,

The quote from your friend shows traces of Artificial Intelligence cut and paste work.

Ask yourself why, in a country that used a decimal system, they would issue savings stamps of 19 centimes.
Also, ask yourself why savings stamps should have a full date.
Finally, ask yourself why someone would waste 94 centimes of savings stamps - just after WWII, when everything, including money, was scarce, to seal an envelope and at the same time use the possibility of free franking.

It does not appear to be a very likely explanation.

As for fiscal stamps: there is no sign of an issuer - strange if it is a local tax -, nor of a purpose.

Finally, the whole answer is quite generic. Savings stamps and fiscal stamps are completely different things. It does not appear to be a very informed answer.

The answer I posted yesterday and subsequently removed was correct and aligns with NSK's valid concerns. I will try and find the information again without using AI and post it. It may take a while.