Ten drobiazg z mosiądzu to rękodzieło.

Because drobiazg is a masculine singular noun in the nominative case.

In Polish, demonstratives like ten / ta / to must agree with the noun they describe:

• ten = masculine
• ta = feminine
• to = neuter

So:

• ten drobiazg = this small item / this trinket
• ta rzecz = this thing
• to rękodzieło = this handicraft

Drobiazg literally means something small or minor. Depending on context, it can mean:

• a small object
• a trifle
• a little decorative item
• sometimes even a detail

In this sentence, it most likely means a small item or trinket. It can sound slightly modest or understated, as if the speaker is referring to it as a little thing rather than something large or important.

Yes. Here z means of / made of / from in the sense of material.

So z mosiądzu means made of brass or of brass.

This is a very common Polish pattern:

• stół z drewna = a table made of wood
• pierścionek ze złota = a ring made of gold
• figurka z brązu = a figurine made of bronze

In your sentence, z mosiądzu describes what the item is made from.

Because after z in the sense of made of / from, Polish uses the genitive case.

The basic dictionary form is:

• mosiądz = brass

But after z here, it changes to:

• z mosiądzu

So the case change is:

• nominative: mosiądz
• genitive: mosiądzu

That is because masculine nouns in the genitive singular can take different endings, often -a or -u. Unfortunately, this is not always fully predictable from English, so you often need to learn the form together with the noun.

For mosiądz, the correct genitive is:

• mosiądzu

This is quite normal for names of materials and substances.

So it is best to learn it as a set:

• mosiądz
• z mosiądzu

In a sentence like this, to links two nouns and works a bit like is in English.

So:

• Ten drobiazg z mosiądzu to rękodzieło.

means something like:

• This brass item is handicraft / a handmade piece.

This structure X to Y is very common in Polish when one thing is being identified or classified as another.

Examples:

• Warszawa to stolica Polski. = Warsaw is the capital of Poland.
• To towarzysz mojego brata. = This is my brother’s companion.

Because Polish very often uses the pattern X to Y instead of X jest Y when one noun is being equated with another.

So:

• Ten drobiazg z mosiądzu to rękodzieło.

is perfectly natural.

If you used jest, you would normally say:

• Ten drobiazg z mosiądzu jest rękodziełem.

That is also correct, but it uses a different structure, and the second noun usually changes case.

Because after to, Polish normally keeps both sides in the nominative case.

So:

• Ten drobiazg z mosiądzu to rękodzieło.

But with jest, the predicate noun is usually in the instrumental:

• Ten drobiazg z mosiądzu jest rękodziełem.

So the difference is:

• X to Y → Y usually stays nominative
• X jest Y → Y is usually instrumental

Because each noun keeps its own grammatical gender.

• drobiazg is masculine
• rękodzieło is neuter

That is completely normal. In Polish, when one noun is identified as another, the nouns do not have to share gender. They are still two separate words with their own grammar.

What must agree with drobiazg is something that directly describes it, such as a demonstrative or adjective:

• ten drobiazg
• mały drobiazg

But rękodzieło does not have to change gender to match it.

Polish has no articles, so there is no direct equivalent of English a or the.

Specificity is shown by:

• context
• word order
• demonstratives like ten

Here, ten makes the noun specific:

• ten drobiazg = this item / this particular small object

Without ten, the sentence would feel more general:

• Drobiazg z mosiądzu to rękodzieło.

That could sound more like a general statement about such an object.

Yes. You could say:

• Ten mosiężny drobiazg to rękodzieło.

That means roughly the same thing.

The difference is mainly stylistic:

• z mosiądzu emphasizes the material
• mosiężny is a normal adjective meaning brass or made of brass

Both are correct. Very often Polish allows either:

• kubek z metalu
• metalowy kubek

It can do both.

Rękodzieło can mean:

• handicraft as a general concept
• a handmade work
• a specific handcrafted item

In this sentence, it means that the object is a handmade piece, not something mass-produced.

So although English might prefer something like a handmade item or a piece of handicraft, Polish can naturally use rękodzieło for the object itself.

Yes, this is a very natural and neutral order.

• Ten drobiazg z mosiądzu to rękodzieło.

Here:

• ten drobiazg = the main thing being talked about
• z mosiądzu = extra information describing it
• to rękodzieło = what it is being identified as

Polish word order is flexible, but changing it usually changes emphasis. The version you have is a straightforward, standard way to say it.