What matters is a padded, velvet-like lining of the slots so that lacquer and fittings do not get scratched; bare wooden slots without padding are unsuitable. Montblanc offers a leather collector's case for 10 writing instruments (item 35819, MSRP 320 euros), and Gutberlet has portfolios for up to 100 pieces. Italian makers such as Visconti, Montegrappa and OMAS used to offer wooden cases with glass lids, but these are now hard to find; offers from the United States are often poor in quality and unattractive due to shipping costs. For retrofitting home-built wooden cases, self-adhesive velvet film (e.g. d-c-fix) is mentioned, with the caveat that plasticisers in PVC films can damage writing instruments over time — it is worth asking the manufacturer about that.