I found an extant gamurra for a pious working class woman in Mantova circa 1496!
Here is the information on Osanna and her dress from Google Art & Culture:
This garment, that the tradition associates to the person of the Blessed Osanna, was a long dress, tight in the upper part and wide at the bottom. It is a white dress made of wool, in part lined with linen, with a tight bust and a high waist, while the bottom part is long and wide; the sleeves are sewn to the rest. It is not necessary to specify the sartorial details, it will be enough to say that the technique used allowed it to be close-fitting. The neckline is oval, quite accentuated, and it is deeper on the back. In fact, in the 15th century, when the dress was made, the back neckline was deeper than the front one. The garment could be defined as a gamurra, a dress made of woollen cloth worn by women in the coldest season. It was a dress generally used for work, so it lacks decorations. It is possible to see this type of dress in many paintings of the 15th century, such as the frescoes in Palazzo Schifanoia in Ferrara. The only unusual detail visible in this item is the colour white, indeed gamurre were generally made with dark cloth. The dress is quite complex and is finely cut. The workshop in which it was made was evidently skilled. On the whole the dress is sombre, as was the life of the Blessed Andreasi. A careful intervention has been carried out with the aim of preventing future deterioration.
Below, a reconstruction of the dress (left) by Thessy Schoenholzer Nichols alongside the original dress (right) worn by Osanna Andreasi.
Does Not Need to Be Hard To Hold by Thessy Schoenholzer Nichols, p. 33
Google Art & Culture