The NanTan FMA3500 is a intel 80486 based notebook computer released in 1991, and came in several different models with several different versions of the intel 486, and primarily used desktop components. It was sold under various brand names including BSI, Eurocom, and AMS. These days the DX models are listed on auction sites as "486 DX Professional" as that's the actual consistent branding printed on the case above the keyboard.
The FMA3500 came in 3 different models: The base level FMA3500, FMA3500SX, and FMA3500C, and it appears it may have been available in all three currently available screen technologies of the time (STN Monochrome, DTSN Color, and Active Matrix TFT Color). These can be told apart by very distinctly different screen bezels (STN = 9.4" Centered, DTSN = 10.4" centered, Active Matrix = 9.4" offset. Palm wrests, hinges, and batteries can differ a little from one another as well based on these and the occasional variation. One of the most distinctive features is the use of desktop components - making this a "baretop" - aka, other companies could order these empty from NanTan and then populate them with their own 3.5" Hard Drives, SIP Memory, 3.5" Floppy Drives, and Socket 1 compatible 486 CPU and sell it as their own models, though these also were apparently sold direct as "NanTan" products themselves at times as well.
These laptops are kind of amusing to enthusiasts and collectors due to their distinctively "out-dated" appearance, looking more like something that would have been a 386SX or a 286 era machine due to the 8.9LB weight, blocky white chassis, the fact the PS/2 port has a TOGGLE SWITCH to turn it on and off, and the battery in back - one of the most distinctive features - is a 12v NiCAD model held on by thumbscrews. Later Active Matrix screen models seem to try and change this by being released in a gray color.
The original (early) units had a 4-pin power adapter connector that is incredibly hard to find a replacement for, but later versions, particularly the FMA3500C, had a regular barrel jack in place of this connector.
Some variations come with a very tiny trackball located above the upper right hand corner of the keyboard - usually moving the "486 DX Professional" logo to the other side. The ball itself is the size of a pea, and rolls on two textured, metal rollers, and acts as a PS/2 device. All variations came with a PS/2 port externally that could be toggled on and off via a Toggle switch on the outside of the case.
- Intel 486 DX-33 (FMA3500, FMA3500C), or 486 SX-25 (FMA3500SX) CPU, Socket 1 (Press-fit)
- AWARD BIOS
- 4x SIP Memory Slots for up to 16MB of RAM, 32MB Maximum theoretical
- 1.44MB 3.5" Desktop floppy Drive
- Standard Desktop 3.5" 40 pin IDE HDD up to 528MB in capacity
- WD VGA Graphics Chipset
- STN Monochrome 9.4", DTSN Color 10.4", or Active Matrix TFT 9.4" LCD Panel 640x480p only
- internal Speaker Sound
- Mechanical Keyboard
- PS/2 Port, switchable via a toggle switch located on the side by the RS232C Serial Port
- 19V NiCAD Battery that attaches to the back of the computer with Thumbscrews
- some later models came with a Trackball built in where the "486 DX" Logo is located.
Expansion was provided via a "Docking Station" that attached in place of the battery with a pair of thumbscrews. This "Docking Station" of sorts provided 2 ISA expansion slots for adding a network card or a sound card to the machine. Apparently this design just predates PCMCIA Type-II slots. The Expansion module connects through an expansion bus connector on the right back corner of the laptop.