Siebe Gorman Mistral Regulator #5132

Siebe Gorman Mistral Regulator (1956–1972): A Rare Vintage Double-Hose Regulator

Introduction

The Siebe Gorman Mistral Regulator, produced from 1956 to 1972, was a single-stage downstream double-hose regulator. Siebe Gorman built it under license from La Spirotechnique, the French company that designed the original Mistral regulator. While similar to the French model, it included unique modifications for British manufacturing.

Collectors and vintage diving enthusiasts seek this historical scuba regulator. Although Siebe Gorman introduced several modifications, the company never documented them. The regulator’s external design remained unchanged, making it difficult to distinguish early versions from later models.

Design and Features of the Siebe Gorman Mistral

The Siebe Gorman Mistral followed the La Spirotechnique Mistral’s design. Its single-stage mechanism delivered reliable airflow while reducing mechanical complexity.

Key Features:

Venturi-Driven Airflow – The Venturi assist system enhanced breathing efficiency.
Double-Hose Configuration – It directed exhaled bubbles behind the diver, improving visibility and reducing noise.
Durable Construction – Siebe Gorman used brass with chrome plating to prevent saltwater corrosion.
Simplified Mechanics – The single-stage design made maintenance easier than two-stage regulators.
Compatibility – It worked with mid-century high-pressure air tanks.

Production Changes and Undocumented Variations

Siebe Gorman modified the Mistral regulator over 12 years but never officially recorded the changes. Unlike other manufacturers, the company did not label updates by model, serial number, or production year.

Notable variations include:

Changes in diaphragm materials
Updated spring and seat configurations
Minor adjustments to Venturi airflow

The Mistral’s Decline and the Rise of Single-Hose Regulators

By the 1970s, divers favored single-hose regulators like the Aqua-Lung Conshelf series. These regulators were smaller, more reliable, and easier to service. As demand declined, Siebe Gorman stopped producing the Mistral in 1972. This marked the end of the single-stage double-hose era.

Why Collectors Value the Siebe Gorman Mistral

Today, the Siebe Gorman Mistral is a rare and valuable diving artifact. Collectors prize it for its historical significance and unique engineering. It remains highly sought-after, especially in Europe and North America.