noun
special make; custom-made; specially manufactured
Refers to an item that is made to order or produced as a special version, distinct from standard mass-produced goods. Often used in product descriptions or manufacturing contexts.
この靴は別製で、通常のモデルより軽く作られています。
These shoes are a special make, made lighter than the standard model.
別製品のため、納期に一か月ほどかかります。
Because it is a custom-made item, delivery will take about a month.
Compound of 別 (separate, special) and 製 (manufacture, make). The reading べっせい follows standard on'yomi. The term is straightforward and likely a relatively modern coinage for specially manufactured goods.