Loli,
Without seeing a picture of your JOHNSON’S® First Aid TRAVELKIT, it sounds as if it might perhaps be from circa the 1930s. (I have a similar half-white, half-blue one in my collection at home that's from the U.S. from that time period.) As the name TRAVELKIT suggests, it was s first aid kit that was small enough for people to take with them in the car, on vacation, etc. If you are able to send me a picture through the blog's e-mail (a link to send an email is in the "About the Author" page of the blog), I will try to identify the date further.
Margaret