A little bit of history
Gauge ‘3’ (or N° 3, as 2½" gauge was originally known) was one of five standard model gauges recommended by a subcommittee of the Society of Model Engineers on February 1st, 1899, making this gauge now more than a century old. At the time, 2½” gauge allowed the construction of fairly successful and reasonably to-scale live-steam locomotives. Number ‘3’ gauge provided enjoyment to those who could afford such indulgences during this period.
Bing and Carette, both Nürnburg-based German toy manufactures, provided locomotives and rolling stock for these standardised gauges, but it was W. J. Bassett-Lowke (who later provided the sole British outlet for German-made products), together with British producers like Jubb, Bonds, The Model Dockyards, and others, who marketed a considerable range of models for gauge ‘3’.
What was of even greater importance in shaping today's 2½" gauge scene was the influence of former engineman, L. Lawrence. His popular writings, under the pseudonym of LBSC, appeared regularly in the Model Engineer and other journals between the mid 1920s and the 1950s. He produced more designs and construction articles for 2½" gauge, coal-fired locomotives than for any other gauge. Most LBSC designs were based on actual prototypes but were not necessarily finished to scale. With this generous exposure, it is not surprising that many of his engines and their derivatives are still around today, together with older engines by Bassett-Lowke, Carson, and their contemporaries.