No direct information but I doubt very much that they were going to be used to manufacture 50,000 81 mm Howitzer, not ammunition for Howitzer but the Howitzer launcher itself. Do you know about any army who possesses 50,000 81 mm Howitzer Launchers?
There is no such thing as an 81 mm "Howitzer launcher". A "howitzer" is a piece of tube/cannon artillery into which you load projectiles and fire them. Basically, its a cannon.
Nobody has claimed that there were intended to be parts for a cannon. They are claimed to be rocket parts, and have nothing to do with howitzers. The difference is enormous, because a rocket, by definition, is a disposable munition. A howitzer is a reusable (obviously) delivery system.
Using the term "rocket" and "howitzer" together is nonsensical, unless you're talking about a very specific type of artillery round that includes a built-in rocket assist. But even then, you're talking about a munition, not a delivery system.
Thank you for the clarification.