Short answer

A Vacheron Constantin Chronomètre clone is graded on four measurements: case diameter, case thickness, lug width, and strap taper. Measure all four with calipers before you judge the rest. Most replica cases for this model land between 38 mm and 40 mm across, with 19 mm or 20 mm lugs. Numbers shift by batch, so treat one listing as one sample.

Case diameter and thickness

The genuine Historiques Chronomètre Royal uses a dress-watch case, and the dial reads large for its size because the bezel is thin. Check bezel width against the dial opening. A wide bezel shrinks the dial and shows in photos. Clone thickness often runs 0.5 mm to 1 mm over the original. Measure from the caseback to the top of the crystal.

Case finish

Look at lug tops, the bezel edge, and the caseband. Original finishing sets polished surfaces against a brushed caseband, or the reverse. Clone flaws cluster at the transitions: soft edges where polish meets brush, rounded lug tips, uneven bevels along the lugs. Caseback engraving is a separate check. Look at letter depth, hallmark placement, and the reference stamp.

Crystal and dial opening

Sapphire should sit flush or stand a little proud, with no gap at the gasket. A domed crystal that rises too far changes the side profile.

Strap details

Original straps are alligator with a matching gold buckle. Clone straps are often calf embossed to look like alligator. Check the scale pattern: real alligator scales vary in size and shape across the strap, and the pattern does not repeat. Check stitch density and thread color. Taper from lug to buckle runs about 20 mm to 16 mm on a 20 mm lug width. Buckle shape matters: the tang, the pin, and the hallmark on the buckle underside.

What strap and case checks do not tell you

Case and strap detail say nothing about the movement. Ask for movement photos as a separate item. If a seller cannot supply them, the listing is incomplete.