Smc,
Sound like great choices in pears though Passe-Crassane is not geared towards most American taste buds . One article says this about Des Urbanistes which I think would be a widely accepted pear anywhere!
"The heirloom fruits are desirable plants for many reasons. When it comes to flavor and quality they’re in a class all their own. There are many kinds of old pears. Of those the Urbaniste is one of the most highly regarded.
Also called Des Urbanistes, this heirloom variety dates to the 1780’s. The tree was found in the garden of the Urbanistes monastery in Mechlin, Belgium, which explains the name. This was found after the order had been disbanded by the authorities. In the neglected garden fruit seedlings came up. This particular one was then introduced by a Belgian pomologist.
This tree was introduced to the U.S. during the early 1800’s. It was first grown by John Lowell in Roxbury, Massachusetts. This was highly recommended by A.J. Downing, author of Downing’s Fruits and Fruit Trees of America, published in 1849. According to Downing, this was a Flemish variety that was introduced by Count de Coloma of Malines and first arrived in the U.S. in 1823.
These are moderately to strong growing trees. They bear large reliable crops, especially as the tree gets older. This will grow in less fertile soil than the Doyenne. It takes some years to begin bearing. This does very well in the Mid-Atlantic. The young, upright shoots are yellow-gray with short joints.
The fruits are medium to large. These vary in shape somewhat from pear-shaped to round or pyramidal. They ripen late, and start ripening at the end of September. They can be stored until November. The smooth yellow skin can have russeting and a light brownish-red blush with streaks and dots. The stalk is an inch long.
Considered a superb dessert quality pear, this was described by A.P. Hedrick in Pears of New York, published in 1921, as “so sweet, rich, perfumed and luscious as to be a natural sweetmeat.” The flesh is mostly white though there can be yellow tinges, especially at the core. Though it is smooth and fairly fine texture, there can be some graininess near the core. The flesh is buttery, tender, juicy, and melting. It has a delicious flavor comparable to Doyenne. This also has a wonder" -The Urbaniste Pear - Landscaping
Similary Passe Crassane or Passe Crassane rouge are excellent quality as you can read about in this French wikipedia page Passe-Crassane — Wikipédia. This is the English translation which gives us insight into why it is banned from growing in France!
"Passe-Crassane is a big winter pear with marbled yellow skin. Its flesh is of excellent quality: quite fine, juicy, melting, pleasantly tart and very fragrant. [personal interpretation]
It is harvested in October.
On sale, it is often presented with a red wax cap at the end of its peduncle . This makes it possible to improve its conservation by limiting the evaporation by this end.
Culture
Formerly the most popular winter pear in France, the Crassane Pass tends to disappear because its tree is very sensitive to fire blight Note 1 , 2 . This sensitivity is not intrinsically superior to that of other varieties (Doyenné du Comice is also very sensitive 3 ) but is due to a production of very abundant and staggered secondary flowering, typical of this variety 4 .
Because of this sensitivity, its planting and propagation have been prohibited in France since 1994 5 , but not the sale of fruit resulting from existing plantations.
Passe-Crassane is one of six varieties of pears from the IGP Pommes et Pears de Savoie .
In Italy, where it is not subject to a multiplication ban, it is one of the ten pears of the Pera dell’Emilia-Romagna appellation. "
You will also enjoy this article http://www.regal.fr/produits/saison/poire-passe-crassane-en-peril-8838 once again translated to English “In 1855, in Rouen, the nurseryman Louis Boisbunel has the idea to cross a pear with a quince . Their child is the crassane passer. She has inherited a little of the physiognomy of her “father”: she is very chubby, almost round, sometimes bumpy. Her skin is yellow marbled with ocher. You will find this pear, rather cheap, from December to April. As with all winter varieties, choose rather firm fruits instead. They will ripen quietly at home, preferably in the open air. The crassane pass is generally recognizable by the red wax cap adorning the end of its tail. This coquetry is, originally, intended to prevent the evaporation of water and, therefore, slow down aging. Becoming useless with the evolution of conservation techniques, wax is now the distinctive seal of this variety. The meat of the crassane pass is granular, which does not please everyone, but also juicy and tart. Nature, it is tasted very ripe, when it is sweeter. This variety is also famous for making excellent jams . And as it gets along very well with spices, you can decline it in many jars (to accompany the brioche of the breakfast as well as the foie gras of the dinner).”