Multi-colour slide pencils of this construction — four coloured leads in a metal body, plus a cap top that screws off to reveal a tube holding spare leads — were in the Montblanc range from the 1930s onwards, and similar designs were built over several decades. The material mark Alpacca on the clip, that is nickel silver, a copper-nickel-zinc alloy containing no silver at all, narrows the date of manufacture to the 1930s through 1960s.
Pencils of this kind were not made in the Montblanc works themselves but to Montblanc's order by the firm of Fend, a supplier specialising in pencil and lead mechanisms. That does nothing to alter their originality, but it does explain why their construction and mechanism differ from the company's own fountain pens. For valuation there is no price list: what counts is the condition, the completeness and the free running of the four slide mechanisms, together with the prices comparable pencils actually fetch. Metal pencils of this sort are regarded as solid everyday items and do not reach the price level of contemporary Meisterstück fountain pens.