During the Middle Ages, Mary Magdalen was believed to have been a repentant prostitute. Crivelli's Magdalen is considerably more wanton in appearance than her fellow female saints.
C. 1474 Montefiore dell'Asso. Detail I interpret this dress as having fancy hook and eye fastenings in front from below the belt to a bit above it. Above that point there are eyes on both sides, with laces running through the lower eyes but not through the top four pairs. Her dress is also laced at the side.
C. 1487 Rijksmuseum. This version has a lower neckline on her underdress. I interpret this dress as closing with fancy hooks and eyes at the wrist and just above the belt, and the top eight pairs of fittings are eyes on both sides, perhaps non-functional. I'm not sure what's happening with the two pairs below them: they might be laced. I believe Crivelli was creating the fittings by stamping them into soft gesso, and that he was using the same stamp for eyes and (used twice) for fastened hooks and eyes.
1491-94 The National Gallery. This could be similar fittings with a higher neckline on the underdress, although since the painting is much smaller and less detailed it's impossible to be sure. The gold dots might be rings rather than fancy eyes, and the underdress might lace all the way to the top.
Saint Catherine of Alexandria
C. 1473, Ascoli. Another Image. Here we can see laces between fancy eyes. They don't go all the way to the top, but the gap revealed is narrow and entirely covered by her underdress.
C. 1476 The National Gallery. I interpret this as a row of fancy hooks and eyes from below her belt to the height of her nipples, and then three pairs of eyes without lacing at the top, revealing a narrow triangle of chemise.
1491-94 The National Gallery. Lacing through eyelets from her belt to the bottom of a v-neck, over a fairly modest underdress. Note the trompe l'oeil fly to her left.
C. 1470, Krakow. Front opening laced through eyelets from the belt to the neckline.
C. 1476 The National Gallery. Similar to the 1476 St. Catherine, but with four pairs of eyes at the top and a slightly lower opening in the overdress.