This it to distinguish it from the signet-1.3-n, pictured below.

https://image.nostr.build/c35246d5966480223f11294724bfc6b42914ab63465c98758c455ea95cdc18d4.jpg#m=image%2Fjpeg&dim=1920x1440&alt=A+blue+USB+device+with+a+matching+blue+button.+This+one+has+bolts+visible+in+the+corners+of+the+case+and+a+loop+has+been+attached+to+hold+it+to+a+keychain.&blurhash=%23fMZ1yax%5EbR.a%23WDR-ocjssmaeR%2BWEWXoJs%2Ca%7DWX%7E2Rn9%24t2Rko0ayWXoej%3Dj%5Dj%5Daxocj%5BWEazaeR.jsNHbIt5WEs.oJa%23NKayoej%40oJR-R%2Bj%3Fs.R-j%5Bs%2CWCayoeWXazWC&x=a06f24a4b48bb708de90f89feb01bef4da51deb655935e6a846573660fb9393d

https://image.nostr.build/71108b49eb08b25f65fbaf7c21943a948dd084d9f545f986b3fd76ee436b855e.jpg#m=image%2Fjpeg&dim=1920x1440&alt=The+bottom+of+that+same+USB+device.+From+this+angle%2C+we+can+see+the+nuts+that+are+flush+mounted+with+the+bottom.&blurhash=%23bLD3aE9%3D%3B-iofs%2BjEa%7Dofs9WEWroIWBR.ofs%2Cax%7E1xBIuR.R-R-R-WDWCt3obWBflt6jZR*bHkCjYofR.NHWBt5oeoIoJWFR%2BjsbIa%7Es%2BWBR-oKWrbHWCj%3Fs-WCoea%23WD&x=0fe7d9575e0b2bccc48aae6107c5e9666dd13b87fb7be418492535a2161ee43a

This is the older model case which had bolts that were visible from the top and required four M2.5 nuts to hold it together.

I thought the nuts would be needed to avoid the screws from stripping out in the plastic case, but it turns out even the test signet-1.3 devices that I've taken apart and put together numerous times have held up just fine.

nostr:nevent1qqstzft7z3axn90ajxjy2p9xdy5lz6f68ujjfeudmjdl5hsqau99k5gpzemhxue69uhkummnw3ezumn0dahx2uewvdhk6q3q6v82nr4xt62nlydtj0mtxr49r6enc5r0sl2f7cq2zwdw7q92j5gsxpqqqqqqzuw7egz
 

 What us this mysterious and wondrous device? 

 Hardward password database. Encrypted, open source, and handmade by yours truly.

Learn more, donate, or buy one here:
https://hax0rbana.org/signet 

 Here's one that's naked!

https://image.nostr.build/713d5e84418abbc1ee6e5dbe218443281dc7f394af8ced301cf9cec87f247d75.jpg#m=image%2Fjpeg&dim=1920x1280&alt=A+USB+device+without+a+case.+The+purple+printed+circuit+board+says+Signet+v1.3.+There+is+a+small+push+button+in+the+center+of+the+board.&blurhash=rTJt%3B%23RQ%7EVozIVoJj%3FWBs%3B%25MxaRjIoofxaWBWVof%252jtM%7Cj%5Bt6ayWVj%5BWCf8WBfiofoLWVWBayj%40t6j%40WCaxWBayofofaxf5WBj%5Ds%3AayWCoLayWC&x=99f4018d751c1c0fe9f1f5d227480e44688fd82ba57274b7b9b1cb6cd336dbac

I guess I'll call that model signet-1.3-naked

nostr:nevent1qqs86hf9unxu8tsny2wuav002nydxken07njp4nqpl22p9tp0syluzgpzemhxue69uhkummnw3ezumn0dahx2uewvdhk6q3q6v82nr4xt62nlydtj0mtxr49r6enc5r0sl2f7cq2zwdw7q92j5gsxpqqqqqqzl2mfh3