Reference Number originally referred to the reference photograph in V&C's archives, which were numbered sequentially by date of entry. Those numbers became useful to refer to a particular model once series production became common, so now a Reference Number is actually a model number. A specific V&C model has several elements; the case and dial, strap or bracelet, and movement calibre. Interestingly, the dial design and case material are quite variable within a single model reference. Your photograph reveals a 12 ligne cal. 477 bumper-wind movement and a guilloche dial of 1950's style. These alone will not establish the reference number of the original watch.
If you have access to the case, the numbers engraved on the inside of the case back may reveal what you want to know. Vintage V&C watches around that period did not always have their reference number engraved on the case - only the case serial number. In those examples, archival or verified auction photos would be required to confirm which model you have. This case back is from a 1950 Ref. 4536 which, as you see, doesn't have the reference number indicated.
In this example, the Reference Number is 6394. This is a non-date model, as the date version would have 6394Q engraved. Below that is the case serial number, which is recorded in the archival records along with the movement serial number and together used by the Patrimony Department to verify authenticity. Below the case number is the case maker's Responsibility Mark, which identifies both the region and manufacturer of this specific case. The same case maker is almost always used for the entire model production.