The 638 S&W’s are now made with the lock. The older models were
made without the lock.

Good evening to you!! The 638 Smith is now made with the lock. Older models were made without. See below link for more information. Hope this helps. Have a good rest of your day.
🇺🇸🇺🇸 'Merica' 🇺🇸🇺🇸
Happy Veterans day 🪖🪖
smith-wesson.com/products/j-frame

No, not all Smith & Wesson Model 638 revolvers come with the internal lock; some are made without it. Smith & Wesson has produced both locked and lock-free versions of their firearms, and they have recently reintroduced models without the lock.
Historical context: For many years, the internal lock was a standard feature on most new Smith & Wesson revolvers, but exceptions were made for some smaller, double-action-only J-frame models.
Recent changes: Smith & Wesson has recently started offering some of their models, including some J-frame revolvers, in "no lock" versions again.
How to tell the difference: You can typically identify a locked model by a small keyhole on the side of the frame, just above the cylinder release. Lock-free versions will not have this feature.

Hi Richard, all current 638 models come with the internal lock. Some earlier models, specifically the 638-2, were produced without it.
Good luck finding one.
Stay safe & have a great day!

Try here: smith-wesson.com/products/j-frame

Hi Richard and welcome. Older, "pre-lock" versions were made without one, and Smith & Wesson has been manufacturing new models with the internal lock. ----- smith-wesson.com/products/j-frame ---------- Cheers and stay safe!