Does Serial mean my razor has a serial number?

No. In the catalogue the word denotes a model designation rather than a serial number, and no key to those designations exists. The dating evidence for the house is its founding date and its lines, not a number.

The maker's archive

Thiers-Issard razors.

Thiers-Issard is a living French house with a confirmed founding date of 1884 and a documented list of owners and acquisitions. That history dates the firm, not the razor: no source found gives a table that turns a Thiers-Issard mark into a year, and the model number on the spine is a model number.

Country: France
Active since
Coverage: 1760–2007 · 3 code systems
Dating tier: Codes only
In the archive: 0 series · 3 code systems · 2 models
Years documented: 1760–2007

Eras

1884–1962

Pierre Thiers

The firm was founded by Pierre Thiers in 1884, and the second generation carried it to 1962.

1985–2007

Reynewaeter and the acquisitions

Gilles Reynewaeter bought the firm in 1985, and the house absorbed further businesses: George Goutte in 1992, Pigeat Taillanderie in 1995, Perard-Dassaud in 2001, Sauzedde-Roddier in 2002 and Bost Chatelet in 2007.

What dates this maker

The tang stamp and the line designations — Singing hollowed 1196, Serial 889, Serial 188, Forged damascus, Historic forged and the seven day sets.
The founding date of 1884 and the ownership events after 1985, which bound the firm rather than the razor.
The country mark MADE IN FRANCE or FRANCE, a lower bound of 1 March 1891 for exports.
The model number on the spine, which is a designation and not a serial number.

Watch out

The word Serial appears in the Thiers-Issard catalogue as a model designation, not as a serial number, which is exactly how the source phrase is written in the data.
The Le Grelot mark sold under this house is a modern line, and a razor carrying it is not automatically old.
No source gives a year table, so the answer is the line plus the firm history, not a date.

Thiers-Issard — tang stamp, lines and continuity (1884 → the present day)1884 → the present day (several generations of owners, from 1985 — Reynewaeter) · 6 rows · High confidence

Country mark (lower bound, NOT a year)the requirement applies from 1 March 1891 (Tariff Act of 1890, also known as the McKinley Tariff) · 2 rows · High confidence

Grind, spine, scales, etching — era markers of a straight razor1700s → mid-1900s · 16 rows · Low confidence

2 Thiers-Issard models are catalogued with their production years, specs and safety notes.