Here is what AI says about this bar tool:

This is a vintage Sheffield-made “The Bar Duzzit” multi-purpose cocktail/bar knife, complete with its original box and illustrated instruction leaflet. It was made in Sheffield, England for the Silvercraft Company. Documentation for this exact model describes it as a combination tool for cutting oranges and lemons, picking up olives, chopping ice and opening bottles.

Description

The piece measures 8 1/2" inches long. The forged stainless-steel blade incorporates several functions:

• serrated cutting edge for citrus and garnishes
• forked/notched tip for picking up olives and fruit
• hook/opening near the handle for bottle-opening duties
• heavy blade suitable for chopping or breaking ice

The blade is etched “Made in / Stainless Steel / Sheffield England.”

The most attractive feature is the shaped porcelain or ceramic pistol-grip handle, decorated with yellow panels, gilt floral ornament and multicolored flowers on a white ground. 

Your original insert reads “THE BAR Duzzit”, “Imported from England,” and identifies the blade as forged stainless steel. An exact Bar Duzzit is documented as a Sheffield product made for Silvercraft, and another boxed Bar Duzzit variant with a sterling handle is known in the collector market.

Age

I would date yours to approximately the 1950s to early 1960s. That is a stylistic estimate based on the packaging, lettering and decorative handle rather than a dated factory record.

Condition

The knife itself appears very good, 

The box and original instruction leaflet are important bonuses. The box shows age and storage wear but remains quite presentable. Complete packaging is much harder to find than the loose knives.