The phrase "a good specimen" is correct and usable in written English.
It can be used when referring to an example or instance that is representative of a particular quality or type, often in scientific or descriptive contexts.
Example: "The biologist presented a good specimen of the rare plant species to the class for study."
Alternatives: "a fine example" or "an excellent sample".
The letter is a good specimen of Basic Mailerese.
But a plant used in this way needs to be a good specimen, well grown.
Unable to hike or boat, I scanned the pond with a pair of binoculars I had remembered to bring, hoping for a good specimen.
We had just discovered the most common mineral on the planet, and, he informed us, it wasn't even a good specimen.
A good specimen can easily run more than $5,000, and often, major trees can fetch upward of $15,000 to $20,000.
By Malcolm Ross The Bell Telephone Laboratories, which is the research department of the American Telephone & Telegraph Company, is a good specimen of the modern invention factory, and handy to anyone who enjoys scientific peepshows.
Root may have eaten his bouillabaisse there long ago, under the regime of the ancienne patronne, a woman known only as Ida, but the du Midi still makes a pretty good specimen now and then.
"Doctor Sleep" is Stephen King's latest novel, and it's a very good specimen of the quintessential King blend.
Except perhaps for far-reaching metaphysical reasons (e.g., an antecedent commitment to idealism), few would deny the very existence of animals, nor the fact that a perfectly good specimen of the species Homo sapiens is presently seated in your chair.
The 19th-century writer Samuel Lewis said that the rebuilt church "forms a very good specimen of the early English style of architecture", adding that it was "effective from its simplicity and the absence of pretension".
At this point, Monsieur Saint-Jour would rake the oysters, collect a few good specimens for sale in port, and remove any parasites that might be endangering his crop.
